Enhanced specificity in immunoscreening of expression cDNA clones using radiolabeled antigen overlay

A highly sensitive and specific method has been developed for immunoscreening clones from an expression cDNA library. The procedures utilize a radiolabeled antigen detection method described originally for the immunoblotting of plasma proteins (5). Screening of rat alpha 1-antitrypsin clones was used. Comparison between Western blots of alpha 1-antitrypsin using both labeled antigen and protein A detection methods showed that the former yielded lower background and greater sensitivity than the latter. Further, this technique was shown to have a lower detection limit of less than 20 ng through Western blot analysis of varying concentrations of alpha 1-antitrypsin. The procedures are based on the expression of the protein by cDNA clones containing the DNA inserts in the correct reading frame. Following the transfer of phage proteins to nitrocellulose membranes, the bivalent antibodies bind monovalently to both nitrocellulose-bound-antigen in the phage lysates and radiolabeled antigen. The radiolabeled antigen overlay method is superior to the protein A detection method in sensitivity, specificity and reproducibility. This improved method can be applied in general for screening expression cDNA libraries, provided that the specific antiserum and radiolabeled antigen are available.

Gender differences of human tissue kallikrein and an erythrocyte kallikrein-like enzyme in essential hypertension

The level of tissue kallikrein in serum and urine, and of an erythrocyte kallikrein-like enzyme, were compared in 10 subjects without hypertension and in 10 patients with hypertension with normal renin levels. Each group consisted of five men and five women. All subjects were observed at a general clinical research center for consecutive 5- to 6-day periods of daily dietary sodium intake of 109, 9, and 259 mEq. Tissue kallikrein levels in serum and urine and levels of the erythrocyte kallikrein-like enzyme were measured with specific radioimmunoassays or with an activity assay, respectively. Mean active and total urinary kallikrein excretion rates were higher in women than in men (both with and without hypertension) when they were given all diets (p less than 0.05 to 0.025), and these rates varied inversely with sodium intake. The serum immunoreactive tissue kallikrein level was higher in men than in women when they were given all diets (p less than 0.05 to 0.001), but there was no difference between subjects with and without hypertension. There were no consistent changes in levels with altered sodium intake. Erythrocyte kallikrein-like esterase activity was greater in women without hypertension than in men without hypertension (p less than 0.05 to 0.001) when receiving the 9 and 109 mEq sodium diets, but values were similar in all groups receiving the 259 mEq sodium diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of the distribution of tissue kallikrein and esterase A, a kallikrein-like enzyme, in rat kidney using specific monoclonal antibodies

Tissue kallikrein (E.C. 3.4.21.35) and arginine esterase A, another closely related, kinin-generating serine protease, have been localized by immunocytochemistry in rat kidney, using monoclonal antibodies that do not crossreact with other kallikrein-related enzymes or with tonin. Kallikrein was present primarily in the apical cytoplasm of the connecting tubule and the cortical collecting duct. Esterase A, on the other hand, was present primarily in the basolateral region of both proximal and distal straight tubules in the outer medulla and medullary rays. In addition, esterase A was demonstrable in distal convoluted tubules and, to a lesser extent, in proximal convoluted tubules. The presence of different kinin-generating enzymes at these sites would permit the formation of kinins from appropriate substrates on both the vascular and luminal poles of separate segments of the kidney tubule.

Molecular cloning and characterization of two rat renal kallikrein genes

Kallikreins compose a multigene family coding for a subgroup of serine proteases, which are involved in the processing of bioactive peptides. Two rat kallikrein-related genes, RSKG-7 (rat submandibular gland kallikrein gene 7) and RSKG-3, have been cloned and their sequences analyzed. RSKG-7 is approximately 4200 bases in length and consists of five exons and four introns. The 5' end region contains the variant CATAT box and TTTAAA box; the 3' end region contains the polyadenylation signal AATAAA. This gene encodes a putative 28,935-dalton preproenzyme of 261 amino acids (aa). The active enzyme consists of 237 aa and is preceded by a deduced signal peptide of 18 aa and a profragment of 6 aa. RSKG-3 is highly homologous to RSKG-7 in terms of its sequence and structure; it encodes a 28,730-dalton prepropeptide consisting of a signal peptide of 18 aa, a profragment of 6 aa, and an active peptide of 235 aa. Sequence comparisons of RSKG-7, RSKG-3, and other kallikrein-related enzymes reveal the key amino acid residues needed for both serine protease activity (His/Asp/Ser) and kallikrein-like cleavage specificity at basic amino acids. Northern blot analyses using specific oligonucleotide probes demonstrate that, among the 12 tissues studied, RSKG-7 and RSKG-3 are expressed in the rat kidney and submandibular gland. Castration of male rats results in a decrease in submandibular gland RSKG-7 mRNA, which can be restored to the normal level by treatment with thyroxine or testosterone. On the other hand, neither castration nor hormonal manipulation affects RSKG-7 mRNA levels in the kidney.

Continuity of care: incorporating patient perceptions

Continuity of medical care has been conceptualized by some researchers as an attitude on the part of the patient and provider rather than as a succession of visits to the same provider. A perception of continuity (PC) scale containing 23 statements was developed to empirically test this conceptualization. A cross-sectional, random sample survey of adult patients in an established suburban family practice utilized a chart review and mailed patient questionnaire to assess the potential value of this scale. The PC scale had a high degree of internal reliability and a greater correlation with patient satisfaction than two commonly used provider continuity measures, even after controlling for demographic variables. The cost of ambulatory primary medical care was not significantly related to any of the continuity measures. The measurement of patient attitudes to define continuity provided information distinct from provider continuity formulas.

A major difference of kallikrein-binding protein in spontaneously hypertensive versus normotensive rats

A unique tissue kallikrein-binding protein was identified and partially characterized in the brain and serum of Sprague-Dawley rats and in the serum-free conditioned media of mouse anterior pituitary cells (AtT 20) and rodent neuroblastoma x glioma hybrids (NG108-15). Kallikrein and kallikrein-binding protein(s) form SDS- and heat-stable complexes with a molecular weight (Mr) of approximately 92,000. The complex formation of 125I-labelled kallikrein and the binding protein in the serum and brain is inhibited by excess unlabelled rat urinary kallikrein, rat arginine esterase A (a kallikrein-like kininogenase), and human urinary kallikrein. When the active site of kallikrein was blocked by phenylmethylsulfonyl fluoride or D-Phe-D-Phe-L-Arg-CH2Cl, no complex formation was detected. Kallikrein-binding protein only forms complexes with active kallikrein or trypsin-activated prokallikrein but not with prokallikrein. 125I-labelled kallikrein forms a 92-kilodalton protein with binding protein in various brain regions of perfused normotensive rats of the Wistar-Kyoto strain (WKY), including the cerebral cortex, cerebellum and brain stem; but complex formation was not found in corresponding brain regions of the spontaneously hypertensive rat (SHR). Similarly, the kallikrein-binding protein was identified in various tissues including thymus, lung, liver, prostate, Cowper's gland, adrenal gland, kidney, and pancreas of WKY rats but not in tissues of SHR. The results suggest a major difference in the kallikrein-binding protein in hypertensive versus normotensive rats. The role of this specific kallikrein-binding protein in cellular hemodynamic processes and blood pressure regulation remains to be investigated.

Immunocytochemical localization of a kallikrein-like serine protease (esterase A) in rat salivary glands

Light and electron microscopic (EM) immunocytochemical methods have been used to localize arginine esterase A, a kinin-generating enzyme immunologically similar to tissue kallikrein, in rat salivary glands. Both polyclonal and monoclonal antibodies to arginine esterase A were used in these studies. By means of a polyclonal antiserum, esterase A was found in granular tubules of submandibular glands and in striated ducts of all three major salivary glands, in a distribution similar to that of tissue kallikrein. With recently developed specific monoclonal antibodies to esterase A, this enzyme was localized in the granules of some (but not all) granular convoluted tubule cells (GCT) and along the basal membranes (but not in apical granules) of striated ducts. By an EM immunoperoxidase method, esterase A was localized subcellularly in granules of some GCT cells and along the basal cell membranes of the tubule and duct system. Thus, this enzyme is found in some sites (GCT granules) shared with tissue kallikrein, but in some unique sites, i.e., basal membranes of striated ducts. The polyclonal antibody used in the present study cross-reacted with tissue kallikrein, but when absorbed with kallikrein, it gave the staining pattern characteristic of monoclonal antibody to esterase A.

Tissue distribution and kininogen gene expression after acute-phase inflammation

A kinin-directed monoclonal antibody to kininogens has been developed by the fusion of murine myeloma cells with mouse splenocytes immunized with bradykinin-conjugated hemocyanin. The hybrid cells were screened by an enzyme-linked immunosorbent assay (ELISA) and a radioimmunoassay (RIA) for the secretion of antibodies to bradykinin. Ascitic fluids were produced and purified by a bradykinin-agarose affinity column. The monoclonal antibody (IgG1) bound to bradykinin, Lys-bradykinin, Met-Lys-bradykinin, and kininogens in ELISA. Further, this target-directed monoclonal antibody recognized purified low and high molecular weight bovine, human, or rat kininogens and T-kininogen in Western blotting. After turpentine-induced acute inflammation, rat kininogen levels increased dramatically in liver and serum as well as in the perfused pituitary, heart, lung, kidney, thymus, and other tissues, as identified by the kinin-directed kininogen antibody in Western blot analyses. The results were confirmed by measuring kinin equivalents of kininogens with a kinin RIA. During an induced inflammatory response, rat kininogens were localized immunohistochemically with the kinin-directed monoclonal antibody in parenchymal cells of liver, in acinar cells and some granular convoluted tubules of submandibular gland, and in the collecting tubules of kidney. Northern and cytoplasmic dot blot analyses using a kinin oligonucleotide probe showed that kininogen mRNA levels in liver but not in other tissues increase after turpentine-induced inflammation. The results indicated that rat kininogens are distributed in various tissues in addition to liver and only liver kininogen is induced by acute inflammation. The target-directed kininogen monoclonal antibody is a useful reagent for studying the structure, localization, and function of kininogens or any protein molecule containing the kinin moiety.

Circulating autoantibodies to mammalian tissue kallikreins

Autoantibodies to tissue kallikrein (EC 3.4.21.35) were discovered in normal human, rat, mouse, and guinea pig sera. Three independent methods--binding of iodolabeled antigen, enzyme-linked immunosorbent assay (ELISA), and immunoblotting--were used to demonstrate these kallikrein autoantibodies. Autoantibodies from rat and human sera were purified, using rat and human tissue kallikrein-affinity chromatography, respectively. Purified rat kallikrein autoantibody bound 50% of 125I-labeled rat urinary kallikrein upon incubation of antibody at 2.5 X 10(-10) M. The subtypes of rat and human kallikrein autoantibodies were determined by an ELISA, using antisera to immunoglobulin subclasses. In both species, autoantibody was predominantly IgG (approximately 80%) and some IgM (approximately 20%). Purified autoantibodies from rat and human sera were separated on sodium deodecyl sulfate-polyacrylamide gels, and their subunits were identified by Western blot analyses, using anti-rat and anti-human IgG antibodies, respectively. When primary cultures of mouse spleen cells were incubated for 1 to 5 days with lipopolysaccharide (1 to 5 micrograms/ml), the anti-kallikrein antibodies in the media increased up to seven-fold. We have demonstrated circulating autoantibodies that recognize and bind both autologous and heterologous kallikrein; however, their significance to the function of the tissue kallikrein-kinin system in normal and disease states remains to be explored.

Identification of latent tissue kallikrein, prolactin and growth hormone secretion in GH3 pituitary cells using modified radioimmunoassays

Our studies demonstrate that rat anterior pituitary cells (GH3) are capable of synthesizing and secreting tissue kallikrein together with prolactin and growth hormone. The secretion of prolactin and growth hormone in GH3 cells was measured by two newly developed sensitive radioimmunoassays (RIA), using the polyethylene glycol separation technique. In the direct radioimmunoassay for rat tissue kallikrein, using a polyclonal antiserum which recognizes both active and prokallikrein, the GH3 kallikrein displays parallelism with standard curves of rat urinary kallikrein. The production of immunoreactive kallikrein, prolactin, and growth hormone is time-dependent, and the levels after a 72 h incubation in serum-free media are approximately 12.2 +/- 4.4 ng, 272.2 +/- 33.0 ng, and 475.6 +/- 4.8 ng per 10(6) cells per ml (mean +/- SD, n = 3), respectively. In Western blot analyses, a specific monoclonal antibody to tissue kallikrein (V4D11) identifies GH3-secreted kallikrein as a approximately 39,000 Da protein, slightly larger than approximately 38,000 Da kallikreins of submandibular gland, mouse anterior pituitary cells (AtT 20) or rodent neuroblastoma X glioma hybrid cells (NG108). Kallikrein mRNA in GH3 cells was identified in Northern blot analyses, using a tissue kallikrein cDNA probe. In a RIA using a kallikrein monoclonal antibody (V1C3) recognizing only active kallikrein, kallikrein could not be detected in the media incubated up to 48 h with GH3 cells. However, after trypsin treatment, a time-dependent increase of immunoreactive kallikrein (using monoclonal antibody V1C3), Tos-Arg-OMe esterase, and kinin-releasing activities can be measured in the conditioned media. The activated esterase activity was inhibited by aprotinin and by affinity-purified kallikrein monoclonal antibody (V4D11) in a dose-dependent manner. The data indicated that rat anterior pituitary GH3 cells secrete latent tissue kallikrein, which can be converted to active kallikrein by trypsin. These hormonally responsive cells co-synthesize kallikrein with prolactin and growth hormone and provide a model system for studying the regulation of kallikrein gene expression.

Identification and expression of kallikrein gene family in rat submandibular and prostate glands using monoclonal antibodies as specific probes

Panels of monoclonal antibodies to three vasoactive peptide-producing enzymes: tissue kallikrein, tonin and arginine esterase A were developed, characterized and used as probes for identification of tissue-specific expression. In addition, immunoblot analyses were performed, using monospecific monoclonal antibodies which did not show cross-reactivity to related-purified enzymes in enzyme-linked immunosorbant assay (ELISA), and radioimmunoassay. We obtained the following results. In rat submandibular gland extract, the expression of 38 kDa kallikrein, 32 kDa tonin, and 18 kDa heavy chain of esterase A was identified by monoclonal antibodies to kallikrein (V4D11), tonin (1F11), and esterase A (5A10, 6C11, and 4B12), respectively. In the prostate gland, a 32 kDa kallikrein-like protein was identified by monoclonal antibodies to esterase A (5A10, 6C11 and 4B12) and by antibodies recognizing both tonin and esterase A (5A5), but not by antibody to kallikrein (V4D11) or to tonin (1F11, 1G6) in Western blot analysis. The esterase A-like enzyme in the prostate gland was found within the cytoplasm of ductal epithelial cells by using monoclonal anti-esterase A antibody (5A10) but not by employing anti-tonin antibody (1F11). These results indicate that tissue kallikrein, tonin, and esterase A are all expressed in the submandibular gland, while only esterase A or an esterase A-like enzyme is expressed in the prostate gland. The specific monoclonal antibodies can be used as probes for the identification and expression of the kallikrein gene-family enzymes.

Abnormal regulation of renal kallikrein in experimental diabetes. Effects of insulin on prokallikrein synthesis and activation

The effects of streptozotocin (STZ) diabetes and insulin on regulation of renal kallikrein were studied in the rat. 1 and 2 wk after STZ injection, diabetic rats had reduced renal levels and urinary excretion of active kallikrein. Tissue and urinary prokallikrein levels were unchanged, but the rate of renal prokallikrein synthesis relative to total protein synthesis was reduced 30-45% in diabetic rats. Treatment of diabetic rats with insulin prevented or reversed the fall in tissue level and excretion rate of active kallikrein and normalized prokallikrein synthesis rate. To further examine insulin's effects, nondiabetic rats were treated with escalating insulin doses to produce hyperinsulinemia. In these rats, renal active kallikrein increased. Although renal prokallikrein was not increased significantly by hyperinsulinemia, its synthesis was increased. As this was accompanied by proportionally increased total protein synthesis, relative kallikrein synthesis rate was not changed. Excretion of active kallikrein was unchanged, but prokallikrein excretion was markedly reduced. Therefore, increased tissue active kallikrein seen with hyperinsulinemia can be explained not only by increased synthesis but also by retention and increased activation of renal prokallikrein. These studies show that STZ diabetes produces an impairment in renal kallikrein synthesis and suggest that this disease state also impairs renal prokallikrein activation. The findings also suggest that insulin modulates renal kallikrein production, activation, and excretion.

Identification of tonin in brain and exocrine tissues and in the cell-free translation products encoded by the mRNA of these tissues

Tissue-specific expression of the esteropeptidase tonin [EC 3.4.99.-] was investigated in rat brain, submandibular gland, pancreas and kidney. Specific polyclonal and monoclonal antibodies to purified rat tonin from the submandibular gland have been developed and characterized and have been purified via a tonin-agarose affinity column. Immunoreactive tonin was measured by a recently developed tonin direct radioimmunoassay using a rabbit tonin antiserum. Resulting tonin levels were found to be 105.27 +/- 2.71 micrograms/mg (of protein) in submandibular gland, 3.18 +/- 0.32 ng/mg in pancreas, 1.35 +/- 0.08 ng/mg in kidney and 0.12 +/- 0.01 ng/mg in brain (means +/- S.E.M.). Western-blot analysis shows that affinity-purified anti-tonin antibody binds to a 32,000-Mr protein from brain and submandibular-gland extracts. The protein, a tonin precursor, was identified from cell-free translation products directly by polyadenylated [Poly(A)+]mRNA species in a wheat-germ system. After the translation products were subjected to immunoprecipitation with affinity-purified tonin antibody, SDS/polyacrylamide-gel electrophoresis of these precipitates revealed two precursors of tonin, with Mr values of 30,000 and 29,000, which are encoded by brain and submandibular-gland mRNA; however, only the 30,000-Mr preprotonin was encoded by pancreas and kidney mRNA. Collectively, the data show that tonin exists in brain, submandibular gland, pancreas and kidney, and can be synthesized by the mRNA of these tissues.

Rat urinary kallikrein localization in kidney: effects of fixation

The influence of fixation on the immunocytochemical localization of tissue kallikrein in the kidney has been evaluated using both monoclonal and polyclonal antibodies. These studies have provided several results relevant to kallikrein localization in kidney: (1) the intensity and distribution of immunostaining with both polyclonal and monoclonal anti-kallikrein antibodies is fixation-dependent; (2) the most intense and consistent localizations of kallikrein are in the connecting tubule and the cortical collecting duct of the nephron; (3) kallikrein-like immunoreactivity is seen in proximal tubules with polyclonal but not with non-cross-reactive monoclonal antibodies; and (4) fixatives which disrupt membranes reveal a kallikrein-like antigen in straight tubules of the outer medulla. However, immunostaining with monoclonal antibodies indicates that much of the observed immunostaining at this site probably represents cross-reactivity with another member of the kallikrein family of enzymes.

Identification and characterization of a tissue kallikrein in rat skeletal muscles

A tissue kallikrein was purified from rat skeletal muscle. Characterization of the enzyme showed that it has alpha-N-tosyl-L-arginine methylesterase activity and releases kinin from purified bovine low-Mr kininogen substrate. The pH optimum (9.0) of its esterase activity and the profile of inhibition by serine-proteinase inhibitors are identical with those of purified RUK (rat urinary kallikrein). Skeletal-muscle kallikrein also behaved identically with urinary kallikrein in a radioimmunoassay using a polyclonal anti-RUK antiserum. On Western-blot analysis, rat muscle kallikrein was recognized by affinity-purified monoclonal anti-kallikrein antibody at a position similar to that of RUK (Mr 38,000). Immunoreactive-kallikrein levels were measured in skeletal muscles which have different fibre types. The soleus, a slow-contracting muscle with high mitochondrial oxidative-enzyme activity, had higher kallikrein content than did the extensor digitorum longus or gastrocnemius, both fast-contracting muscles with low oxidative-enzyme activity. Streptozotocin-induced diabetes reduced muscle weights, but did not alter the level of kallikrein (pg/mg of protein) in skeletal muscle, suggesting that insulin is not a regulator of kallikrein in this tissue. Although the role of kallikrein in skeletal muscle is unknown, its localization and activity in relation to muscle functions and disease can now be studied.

Tissue kallikrein in rat brain and pituitary: regional distribution and estrogen induction in the anterior pituitary

We have detected tissue kallikrein and kallikrein mRNA in various brain regions with a kallikrein direct RIA and with nucleic acid hybridization using a kallikrein cDNA probe. In the direct RIA, rat urinary kallikrein-like activity was found in the pituitary and pineal glands, hypothalamus, cerebral cortex, cerebellum, and brain stem. Pituitary and pineal gland kallikrein concentrations were significantly higher than those in other regions. Only in pituitary was there a significant difference in tissue kallikrein concentration according to sex, with glands from female rats showing levels 4-fold higher than those from male rats. Kallikrein mRNAs were detected in all of the regions and were about 4-fold higher in female than in male pituitary gland. Northern blot analyses show sex dimorphism of pituitary kallikrein mRNA, similar in size to submandibular gland and kidney mRNA. In castrated male rats, whole pituitary kallikrein content was reduced to 50% of the control value and increased 1.7-fold with testosterone replacement and 18-fold with 17 beta-estradiol treatment. Neither T4 nor cortisol affected whole pituitary kallikrein levels in the castrated male rat, but testosterone decreased pituitary kallikrein in normal female rats by 35%. When anterior pituitary or neurointermediate lobe extracts were separately examined, immunoreactive kallikrein was 10.2- and 1.3-fold higher respectively, in female than in male rat lobes. Estradiol benzoate (30 micrograms/kg) administration increased kallikrein levels 90- and 22-fold, respectively, in the anterior pituitary of gonadectomized male and female rats, while it increased by only 40-50% kallikrein levels in the male and female neurointermediate lobe. In dot blot analysis, kallikrein mRNA levels were increased 5-fold by 17 beta-estradiol in the whole pituitary of castrated male rats. In the cytoplasmic dot hybridization analysis, estradiol benzoate treatment increased kallikrein mRNA levels 54-fold in the anterior pituitary of ovariectomized rats. The data show that a tissue kallikrein indistinguishable thus far from a urinary kallikrein is widely distributed in brain and pituitary and that levels of enzyme and mRNA are comparable in certain central sites. Kallikrein levels in the anterior and neurointermediate pituitaries are differentially regulated by estrogen.

Structural organization of apolipoprotein B-100 of human plasma low density lipoproteins. Comparison to B-48 of chylomicrons and very low density lipoproteins

The present study characterizes the substructural organization of apolipoprotein B-100 (B-100) of human plasma low density lipoproteins (LDL) and its relation to B-74 and B-26 of LDL and B-48 of chylomicrons and very low density lipoproteins. LDL were digested with human kallikrein and thrombin to yield two major fragments: K1 (Mr 410,000) and K2 (Mr 145,000) and T1 (Mr 385,000) and T2 (Mr 170,000), respectively. The antigenic sequences, Mr, and amino acid compositions of K1 and K2 were identical to those of plasma B-74 and B-26; B-26 and K2 had identical NH2-terminal sequences and correspond to the NH2-terminal region of B-100. K1 was further degraded by kallikrein to give K3 (Mr 235,000) and K4 (Mr 170,000); these peptides correspond immunochemically to two newly discovered plasma LDL peptides B-44 and B-30 and are assigned as complementary fragments of B-74. The thrombin cleavage fragments, T1 and T2, did not correspond to B-74 and B-26. Neither kallikrein nor thrombin generated a fragment from B-100 corresponding to B-48 in chylomicrons. However, B-48 showed antigenic homology with B-26 and to the of B-74 adjoining B-26, indicating that its structure is represented in the NH2-terminal half of B-100. The structural studies further clarify the relatedness among the B-100, B-74, B-26, and B-48 polypeptides and should now make possible the delineation of the functional domains mediating the interactions of apolipoprotein B in the circulation and arterial wall.

Characterization of malignant peripheral blood cells of juvenile chronic myelogenous leukemia

Characterization studies were performed on the malignant peripheral blood cells from three patients with juvenile chronic myelogenous leukemia (JCML) by allowing the cells to increase numerically in liquid cultures. JCML cells proliferated rapidly and excessively in the absence of an added humoral growth factor, whereas control peripheral blood cells declined in number when cultured under identical conditions. Clonality of JCML cells was proven by cytogenetic analysis of the proliferating population. JCML cells were exclusively of monocytic lineage as determined by morphology, staining characteristics, and monoclonal antibody identification of cell-specific surface antigens, but cytochemical and functional studies identified aberrant properties indicating defective differentiation. Striking differences from control cells in ultrastructure and topography were also observed by transmission and scanning electron microscopy. These data provide new information on the cellular origin of JCML and form the basis for further study of leukemic cell biology in this disease.

Identification of a new tissue-kallikrein-binding protein

We have identified a tissue-kallikrein-binding protein in human serum and in the serum-free culture media from human lung fibroblasts (WI-38) and rodent neuroblastoma X glioma hybrid cells (NG108-15). Purified and 125I-labelled tissue kallikrein and human serum form an approximately 92,000-Mr SDS-stable complex. The relative quantity of this complex-formation is measured by densitometric scanning of autoradiograms. Complex-formation between tissue kallikrein and the serum binding protein was time-dependent and detectable after 5 min incubation at 37 degrees C, with half-maximal binding at 28 min. Binding of 125I-kallikrein to kallikrein-binding protein is temperature-dependent and can be inhibited by heparin or excess unlabelled tissue kallikrein but not by plasma kallikrein, collagenase, thrombin, urokinase, alpha 1-antitrypsin or kininogens. The kallikrein-binding protein is acid- and heat-labile, as pretreatment of sera at pH 3.0 or at 60 degrees C for 30 min diminishes complex-formation. However, the formed complexes are stable to acid or 1 M-hydroxylamine treatment and can only be partially dissociated with 10 mM-NaOH. When kallikrein was inhibited by the active-site-labelling reagents phenylmethanesulphonyl fluoride or D-Phe-D-Phe-L-Arg-CH2Cl no complex-formation was observed. An endogenous approximately 92,000-Mr kallikrein-kallikrein-binding protein complex was isolated from normal human serum by using a human tissue kallikrein-agarose affinity column. These complexes were recognized by anti-(human tissue kallikrein) antibodies, but not by anti-alpha 1-antitrypsin serum, in Western-blot analyses. The results show that the kallikrein-binding protein is distinct from alpha 1-antitrypsin and is not identifiable with any of the well-characterized plasma proteinase inhibitors such as alpha 2-macroglobulin, inter-alpha-trypsin inhibitor, C1-inactivator or antithrombin III. The functional role of this kallikrein-binding protein and its impact on kallikrein activity or metabolism in vivo remain to be investigated.

Age and hormonal dependence of tonin levels in rat submandibular gland as determined by a new direct radioimmunoassay

A simple and sensitive direct radioimmunoassay for tonin (EC.3.4.99.-) has been developed. This assay incorporates a modified and convenient poly(ethylene glycol) technique for separation of free from bound tonin. A rabbit antiserum in a final dilution of 1:160,000 was used and the purified tonin was labelled with 125I by using a lactoperoxidase method. It detects 20 pg of immunoreactive tonin per tube. Serial dilutions of rat submandibular gland extracts showed complete parallelism with tonin standard curves. No cross-reactivity with rat tissue kallikrein was seen. Intra- and inter-assay errors were 3.2 and 5.6%, respectively. Using this assay, immunoreactive tonin was detected in the rat submandibular gland as early as 3 weeks after birth (body wt. approximately 50-60 g). Tonin levels are shown to be dependent on age and sex with significantly higher levels in male than in female rats. Castration results in decrease of tonin levels and 17 alpha-methyltestosterone replacement reversed the level to higher than the sham-operated control rats. Cortisol treatment increased, but thyroxine or oestradiol had no effect, on tonin levels in the submandibular gland of castrated rats. This newly developed radioimmunoassay can now be used to measure low levels of tonin in various tissues and body fluids to address questions about its regulation and functional significance.

Ocular distribution of keratan sulfates during pre- and postnatal development in rabbits

Twenty-six monoclonal antibodies (MAbs) developed against rabbit corneal proteokeratan sulfate (PKS), were used to evaluate immunohistochemically the ocular distribution of PKS during prenatal and early postnatal development in rabbits. These MAbs were directed against epitopes located in the keratan sulfate (KS) chains of the proteoglycan (SundarRaj et al., 1985). Staining of cryostat sections of the eyes was carried out using an indirect peroxidase-conjugated technique. Only one of the MAbs reacted with the presumptive corneal region at day 13 or 16 of fetal development. By day 20, more MAbs reacted with the corneal stroma. There were distinct differences, however, in the distribution of the epitopes recognized by the various MAbs. A few of them stained only the posterior region of the cornea, whereas others showed a decreasing staining gradient from the posterior to the anterior region. By day 24, all of the MAbs reacted with the corneal stroma, but some reacted also with the limbal region and with the conjunctival stromal matrix. One MAb also reacted with the conjunctival epithelial layer, but only at this stage of development. Conjunctival staining was more intense at day 28 of fetal development and at day 2 postnatally. KS was not detectable in the conjunctiva of adult rabbits with any of the MABs. These results suggest that although KS synthesis starts at very early stages of fetal development, there are progressive changes in its antigenic structure in specific regions of the cornea and conjunctiva during corneal development.

Sex dimorphism and hormonal regulation of rat tissue kallikrein mRNA

The regulation of rat tissue kallikrein mRNA levels was investigated by RNA filter hybridization using a kallikrein cDNA probe and by in vitro translation of isolated RNA. The synthesis of a 37 kDa polypeptide has been hybrid-arrested by the tissue kallikrein cDNA in cell-free translation assays directed by submandibular mRNA and the quantitation of this protein was used as a measure of translational activity of kallikrein mRNA. In Northern blot analyses, relative kallikrein mRNA levels were found to be 60-fold higher in submandibular gland than in pancreas and 20-fold higher than in kidney. In addition, it was noted that kallikrein mRNA is differentially regulated in tissues from male and female animals. Rat submandibular gland kallikrein mRNA is 2-times more abundant in male animals as in females. This trend is reversed in kidney, where the kallikrein mRNA in females is twice that in male animals. Relative submandibular gland kallikrein mRNA levels were found to be responsive to hormonal manipulation as measured by both Northern blotting and cell-free translation assays. Castration of male animals resulted in a decrease of kallikrein mRNA which could be partially restored by treatment with thyroxine and almost completely restored by testosterone treatment. The submandibular gland kallikrein mRNA in normal female rats was increased up to 30% by administration of testosterone or thyroxine. Adrenalectomized female rats showed a decrease in submandibular kallikrein mRNA which was significantly increased by testosterone, thyroxine, aldosterone and cortisol, with the largest effect being a 2- to 2.4-fold increase in cortisol-treated rats. These results indicate that hormones regulate tissue kallikrein synthesis in the rat submandibular gland, at least in part, by altering kallikrein mRNA accumulation.

Immunological identification of rat tissue kallikrein cDNA and characterization of the kallikrein gene family

A tissue kallikrein cDNA was identified by direct immunological screening with affinity-purified anti-rat tissue kallikrein antibody from a rat submandibular cDNA library constructed with the expression vector pUC8. Sequence analysis of the kallikrein cDNA revealed an encoded protein 97% homologous to the partial amino acid sequence of rat submandibular kallikrein. This cDNA was used to hybrid-select kallikrein-specific RNA from submandibular gland. Translation of the hybrid-selected RNA in a cell-free assay system resulted in the production of a 37 kDa peptide representing the preproenzyme. In addition, hybrid-selection of RNA under less stringent conditions showed cross-hybridization with other submandibular gland mRNA species. In correlation with these results, analysis of rat genomic DNA showed extensive hybridization, suggesting a family of closely related kallikrein-like genes. Consequently, a Charon 4A rat genomic library was screened for kallikrein genes by hybridization with rat tissue kallikrein cDNA. Thirty-four clones were isolated and found to be highly homologous by hybridization and restriction enzymes analyses. Fourteen unique clones were identified by restriction enzyme site polymorphisms within DNA segments which hybridized to the kallikrein cDNA probe and it was estimated that at least 17 different kallikrein-like genes are present in the rat. Sequence and structural analysis of one of the genomic clones revealed a gene structure similar to that of other serine proteinases. Comparison of the partially sequenced exon regions of the gene with the sequence of rat tissue kallikrein cDNA reveals 89% identity when aligned for the greatest homology. However, the genomic sequence predicts termination codons in all three translational reading frames, implying that this gene is nonfunctional, i.e., a pseudogene. Comparison of the rat genomic sequence to a kallikrein-like gene from the mouse reveals extensive preservation of exons, less identity within introns and no significant homology between extragenic regions.

A monoclonal antibody to rat tissue kallikrein: use in biochemical and immunohistochemical studies

A monoclonal antibody (V4G6) to rat tissue kallikrein (EC 3.4.21.35) has been developed and characterized. This clone showed no cross-reactivity with rat tonin, rat esterase A or human urinary kallikrein in either radioimmunoassay or enzyme-linked immunosorbent assay. The monoclonal antibody used in the direct radioimmunoassay detects purified rat urinary kallikrein in a range of 0.32 to 40 ng per tube. The displacement curves for rat submandibular gland, pancreatic and kidney extracts and urine were parallel with the standard curve of purified rat urinary kallikrein. Analysis of immunoprecipitates from [14C] DFP labeled submandibular gland extract with SDS-polyacrylamide gel electrophoresis, demonstrates that this antibody recognizes only one 38,000 dalton serine protease while polyclonal antiserum identifies multiple species. Using this specific monoclonal reagent, tissue kallikrein was localized immunohistochemically in the granular convoluted tubules and striated ducts of the rat submandibular gland and in the acinar cells of the rat pancreas. The results showed that the monoclonal antibody (V4G6) can specifically recognize a single kallikrein in the tissue extracts without cross-reacting with other kallikrein-related serine proteases. This monoclonal antibody can be used as a specific reagent for quantitation, identification and immunohistochemical studies of tissue kallikrein.

Active kallikrein, preprokallikrein, and kallikrein-inhibitor complex

Active kallikreins isolated from various exocrine and endocrine tissues were identified by a monoclonal antibody in Western blot analyses to be approximately 38,000 dalton proteins. Kallikreins isolated from rat pancreas, kidney, submandibular gland, brain, spleen and urine were indistinguishable with respect to molecular weight and immunological characteristics. Preprokallikreins were synthesized in a cell-free translation system directed by mRNAs and immunoprecipitated by affinity-purified kallikrein antibody. Analysis of the precipitates by SDS-polyacrylamide gel electrophoresis revealed a approximately 37,000 dalton polypeptide in kidney, brain and submandibular gland translation products. This 37,000 dalton kallikrein precursor was hybrid-arrested by a kallikrein cDNA encoding tissue kallikrein which was isolated from a rat submandibular gland cDNA library. The immunoprecipitates of products directed by pancreatic mRNA showed a major protein with Mr of approximately 30,000. An endogenous approximately 92,000 dalton component in rat urine and kidney was also identified by a monoclonal antibody to tissue kallikrein and represents a kallikrein-inhibitor complex. These results indicate that tissue kallikreins can be initially synthesized as 37,000 or 30,000 dalton prepropeptides and then converted into a 38,000 dalton active form by proteolytic processing and glycosylation. The active kallikrein is capable of binding to an inhibitor to form a 92,000 dalton complex.

Kallikrein localization in rat brain by immunohistochemistry

Using an antibody-peroxidase bridge technique with either polyclonal antibodies or a specific monoclonal antibody, immunoreactive kallikrein was localized in all three lobes of the pituitary, in ependymal cells lining the third ventricle, and in cell bodies of the following hypothalamic neuronal nuclei: supraoptic, arcuate, paraventricular and ventromedial.

An improved method for the measurement of rat tissue kallikrein using a monoclonal antibody which recognizes only active enzyme

We have used a monoclonal antibody which recognizes active kallikrein to develop a method for measurement of inactive and active kallikrein in rat urine. The inactive kallikrein levels were calculated from the difference between values before and after trypsin pretreatment in the kallikrein direct radioimmunoassay. In this assay, the final dilution of ascitic fluid containing monoclonal antibody was 1:1.6 X 10(7) which gave 35% specific binding to 125I-labelled kallikrein, and the minimal detectable amount was 0.08 ng/tube. When inactive kallikrein was assessed by this method and a kininogenase assay in 23 randomly collected urines, a significant correlation was observed between the values obtained from the two assays (p less than 0.01). The regression line for this relation was similar to that observed between purified active kallikrein concentration and kininogenase activity. The active and inactive kallikrein excretion rates and the inactive/total kallikrein ratio in rats on normal sodium diet were 74.0 +/- 17.3 micrograms/day (m +/- SD), 82.8 +/- 14.4 micrograms/day and 53.1 +/- 7.1%, respectively. This method can now be applied to studies of prokallikrein activation.

Processing of apolipoprotein B-100 of human plasma low density lipoproteins by tissue and plasma kallikreins

Human plasma low density lipoproteins (LDL) are the major carriers of cholesterol and cholesteryl esters in the circulation. Their increased levels correlate positively with increased risk of coronary artery disease. LDL contain a single major apolipoprotein of apparent molecular weight (Mr) = 550,000, designated apolipoprotein B-100 (apoB-100), and in some LDL preparations, minor components termed apoB-74 (410,000) and apoB-26 (145,000). The structural relationship of the apoB-74 and -26 proteins to the apoB-100 has remained obscure and their roles in cholesterol metabolism are unknown. In the present study, we show that the addition of kaolin to plasma anticoagulated with EDTA induces the proteolytic cleavage of apoB-100. As a result, two apoB peptides are produced with Mr indistinguishable from plasma apoB-74 and -26. The specific cleavage of apoB-100 was mimicked in vitro by purified human plasma and tissue kallikreins. In contrast, thrombin, factor Xa, plasmin, trypsin, and chymotrypsin did not produce these peptides when incubated with LDL. The findings of the study suggest that apoB-74 and -26 are proteolytic fragments of apoB-100 and that the endogenous protease has a kallikrein-like specificity for DLD-apoB-100. The role of plasma and tissue kallikreins in cholesterol metabolism remains to be determined.

Characterization of rat kallikrein-like multigene family and its expression in the submandibular gland

A cDNA clone encoding rat tissue kallikrein was isolated from a submandibular cDNA library. The kallikrein cDNA clone was used as a probe to analyze the complexity of the kallikrein-like gene family and its expression. The results indicate that rat kallikrein-like genes identified with this probe belong to a very large and highly homologous multigene family. A number of these genes, perhaps as many as a dozen or so, are expressed in the submandibular gland.

Characterization of monoclonal and polyclonal antibodies to human tissue kallikrein

Monoclonal antibodies to purified human urinary kallikrein have been developed. Selection of antibody producing clones was based on 125I-kallikrein binding activity of hybridoma media in both radioimmunoassay and enzyme-linked immunosorbent assay. Three clones (2 IgG1, 1 IgG2b) were subcloned, characterized, and compared with the polyclonal antiserum generated in rabbits immunized with the purified kallikrein. With radioimmunoassay, mouse ascitic fluids or rabbit antisera dilutions showing 50% binding to 125I-kallikrein were 1:1.2 X 10(6) (E7A9), 1:1.2 X 10(5) (H6A6), 1:8.0 X 10(4) (E12H1), and 1:1.4 X 10(6) (the rabbit antisera). With enzyme-linked immunosorbent assay, mouse ascitic fluids from clones E7A9 and H6A6 showed half-maximal absorbance at dilutions of 1:2.1 X 10(5) and 1:1.0 X 10(5) respectively, and the polyclonal antiserum showed half-maximal absorbance at a dilution of 1:2.0 X 10(4). These monoclonal antibodies showed no cross-reactivity with rat tissue kallikrein, rat urinary plasminogen activator, or dog pancreatic kallikrein, while the polyclonal antiserum showed some cross-reactivity. The binding of monoclonal or polyclonal antibodies to 125I-human urinary kallikrein was not affected by human plasma kallikrein, thrombin, or urokinase in a competitive radioimmunoassay. By using purified human urinary kallikrein immobilized to agarose, antibodies produced by clones E7A9 and H6A6 and in the rabbit antisera were purified to homogeneity. Each of these affinity-purified antibodies inhibited the esterase activity, and two of the three inhibited the kininogenase activity, of human urinary kallikrein. A sandwich immunosorbent assay was developed to measure this kallikrein using monoclonal antibody from the clone E7A9 in conjunction with the polyclonal antibodies.(ABSTRACT TRUNCATED AT 250 WORDS)

Specific identification of tissue kallikrein in exocrine tissues and in cell-free translation products with monoclonal antibodies

A panel of six mouse monoclonal antibodies (IgG1) has been prepared against purified rat urinary kallikrein (EC 3.4.21.35) and characterized. In radioimmunoassay, the antibody titres of ascitic fluid giving 50% binding to 125I-kallikrein range from 1:2 X 10(3) to 1:1 X 10(6). Antibodies from four of the clones show no cross-reactivity with human urinary kallikrein, rat urinary esterase A or tonin. However, antibodies from a fifth clone cross-react with tonin and, from a sixth, with both urinary esterase A and tonin. Three of the kallikrein affinity-purified monoclonal antibodies inhibited, whereas one of the antibodies stimulated, kallikrein activity. Tissue kallikrein from rat submandibular-gland and pancreatic extracts and urine were labelled with [14C]di-isopropyl phosphofluoridate, immunoprecipitated with each of the six monoclonal antibodies and identified to be 38 kDa proteins, similar in size to purified rat urinary kallikrein. Western-blot analysis shows that 125I-labelled kallikrein monoclonal antibodies (V4D11) bind directly to a 38 kDa protein in submandibular-gland and pancreatic extracts and urine. Cell-free translation products of submandibular-gland polyadenylylated[poly(A)+]mRNA were immunoprecipitated with affinity-purified sheep anti-kallikrein antibodies and three monoclonal antibodies (V4D11, V4G6 and V1C3). Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis of these immunoprecipitates revealed that two kallikrein precursors with Mr values of 37 000 and 35 000 are encoded by submandibular-gland mRNA. The third monoclonal antibody, V1C3, which binds to active kallikrein, did not recognize either precursor form. Collectively, the data show that these monoclonal antibodies comprise a set of powerful and specific reagents for studies of tissue kallikreins.

Immunocytochemical localization of tissue kallikrein in brain ventricular epithelium and hypothalamic cell bodies

A specific monoclonal antibody against rat tissue kallikrein was used as the primary antibody for indirect immunoperoxidase staining of rat hypothalamus. Kallikrein was localized in the epithelial cells (ependyma) lining the third ventricle as well as in cell bodies of arcuate, supraoptic, paraventricular, and ventromedial nuclei.

Immunological analysis of rat pancreatic prokallikrein activation

The present study shows that tissue kallikrein is present in rat pancreas as a proenzyme that can be converted by autolysis to a 38 000 Da active enzyme. The activation of pancreatic prokallikrein was examined by direct radioimmunoassay, enzymatic assays, active-site labeling with immunoprecipitation, and Western blot analyses. A monoclonal antibody (V1C3), which binds only active kallikrein, was used in a direct radioimmunoassay to monitor the appearance of the active enzyme. During a 22-h autolysis of pancreatic extract, a time-dependent increase in active kallikrein concentration paralleled the increase of kallikrein activities measured by both TosArgOMe esterase and kininogenase assays. The activation process was further analyzed by labeling the pancreatic extract with [14C]diisopropylphosphorofluoridate [( 14C]DFP) followed by immunoprecipitation with sheep anti-kallikrein antiserum. Pancreatic prokallikrein was not labeled by [14C]DFP; however, upon autolysis, a 38 000 Da active kallikrein can be labeled with [14C]DFP and increase in quantity with time. Western blot analysis, using a monoclonal antibody (V4D11) which recognizes both latent and active tissue kallikreins, identified a 39 000 Da pancreatic prokallikrein prior to autolysis and a 38 000 Da active kallikrein after 7 h of autolysis. The results indicate that the pancreatic prokallikrein exists as a 39 000 Da protein which may be converted to a 38 000 Da active kallikrein, indistinguishable from purified urinary, brain, spleen or submandibular gland kallikrein.

Isolation of tissue kallikrein in rat spleen by monoclonal antibody-affinity chromatography

Rat spleen kallikrein was identified and purified by DEAE-cellulose and monoclonal antibody-affinity chromatography. The purified enzyme has Tos-Arg-OMe esterase activity and kinin-releasing activity from a purified low-molecular-weight kininogen substrate. In the direct radioimmunoassay for tissue kallikrein, the splenic enzyme displays parallelism with standard curves of rat urinary kallikrein. The pH profiles of the Tos-Arg-OMe esterase activities of spleen and urinary kallikrein were identical with optima at 9.0. Rat spleen kallikrein was inhibited strongly by aprotinin and affinity-purified kallikrein antibody and weakly by soybean trypsin inhibitor. The IC50 values were similar to those observed against rat urinary kallikrein. Neither the urinary nor the splenic enzyme was inhibited by lima bean trypsin inhibitor or preimmune serum immunoglobulins. Spleen kallikrein was labeled with [14C]diisopropylphosphorofluoridate and visualized by fluorography on a sodium dodecyl sulfate-polyacrylamide gel. The electrophoretic mobility of the splenic enzyme was indistinguishable from that of urinary kallikrein A with an estimated Mr of approx. 38 000. With Western blot analyses using a rabbit anti-kallikrein antibody followed by 125I-labeled protein A binding, the spleen and urinary kallikreins were again visualized at identical positions by autoradiography. The data show that there is a rat splenic tissue kallikrein which is indistinguishable from a renal kallikrein with respect to physicochemical properties, immunological character and susceptibility to inhibitors.

Degradation of apolipoprotein B-100 of human plasma low density lipoproteins by tissue and plasma kallikreins

Human plasma low density lipoproteins (LDL) contain one major apoprotein of apparent Mr = 550,000 designated apolipoprotein B-100 (apo-B-100) and in some LDL preparations, minor components termed apo-B-74 (Mr = 410,000) and apo-B-26 (Mr = 145,000). The structural and metabolic relationships among these LDL apoproteins remain obscure. In the present study, we show that the mixing of proteolytic inhibitors with blood at the moment of collection prevents the appearance of apo-B-74 and -26 in plasma LDL indicating that these peptides are derived by proteolytic degradation of apo-B-100. In order to simulate the degradation in vitro, LDL were digested with plasmin, trypsin, chymotrypsin, thrombin, and tissue and plasma kallikreins and the degradation products analyzed by polyacrylamide gradient gel electrophoresis. While plasmin, trypsin, and chymotrypsin caused extensive degradation of apo-B-100, thrombin, and tissue and plasma kallikreins generated limited cleavage patterns. LDL digested with thrombin contained stoichiometric amounts of two peptides with apparent Mr = 385,000 and 170,000. Mixing experiments showed that the thrombin-derived peptides of apo-B-100 did not co-migrate with apo-B-74 and B-26 during electrophoresis indicating that these peptides were different. In contrast, LDL digested with kallikrein contained stoichiometric amounts of two peptides with apparent molecular weights identical to apo-B-74 and -26. Together, the above results indicate that apo-B-74 and -26 are degradation products of apo-B-100 and are not produced by the action of thrombin. Whether the expression of a kallikrein-like activity in vivo accounts for the specific degradation of LDL B-100 to yield LDL B-74 and -26 remains to be determined.

Immunoglobulin gene rearrangements in hairy cell leukemia

Studies of hairy cell leukemia have yielded conflicting data about the cell of origin in this disease. To investigate this issue, we have examined the state of immunoglobulin genes in the cells of 11 randomly selected spleens showing histologic involvement with hairy cell leukemia. DNA was extracted from splenic tissue samples and digested with restriction endonucleases. Following agarose gel electrophoresis and transfer to nitrocellulose filters or activated nylon membranes, splenic DNA was hybridized with radiolabeled DNA fragment probes specific for the constant regions of the immunoglobulin heavy chain and kappa and lambda light chain genes. Autoradiograms of the hybridized DNA in each case revealed rearrangements of a heavy chain gene and at least one light chain gene. In addition, immunophenotyping of cellular immunoglobulin polypeptides was carried out on frozen tissue sections from all but one case. In each case in which an immunoglobulin polypeptide could be detected, a rearrangement was present in the DNA of the corresponding immunoglobulin gene. These studies offer strong evidence for endogenous immunoglobulin synthesis in hairy cells and for the B lymphocytic character of this leukemia.

Identification of a kallikrein-like latent serine protease in human erythrocyte membranes

We have discovered and characterized a kallikrein-like latent serine protease in intact human erythrocytes and ghosts. The enzyme is activatable by trypsin. The solubilized enzyme has esterolytic activity with a pH optimum of 9; but the membrane-associated activity increases almost linearly up to pH 10. The activated enzyme releases kinin from bovine low molecular weight kininogen. Enzyme activity is inhibited by TosLysCH2Cl , phenylmethylsulfonyl fluoride, aprotinin and amiloride, and weakly by soybean or lima bean trypsin inhibitor. It is inhibited by Co2+, Zn2+ and Mn2+ but is stimulated by Fe2+, deoxycholate and phospholipase A2. An erythrocyte membrane protein (Mr = 88,000) with an active site serine residue was identified with [14C]-diisopropylphosphorofluoridate labeling. Consistent with the finding of tryptic activation of the latent erythrocyte serine protease, trypsin treatment reduced the density of labeling of this protein and revealed a lower molecular weight form (Mr = 64,000). Possible relationships between the activity of this newly identified serine protease and events such as erythrocyte membrane ion fluxes might be of interest.

Tissue kallikrein synthesis and its modification by testosterone or low dietary sodium

A method has been developed to measure the relative rate of rat tissue kallikrein synthesis which employs a specific antiserum raised against a purified rat urinary kallikrein. Incorporation of [35S]methionine into kallikrein and protein 20 min after intraperitoneal injection was measured in submaxillary gland, pancreas, kidney and descending colon. Kallikrein content was measured with a direct radioimmunoassay, and kallikrein-specific incorporation of [35S]methionine measured after immunoprecipitation. Kallikrein specific radioactivity (c.p.m./mg of enzyme) was about 100-fold greater than that in total protein in both kidney and colon. In contrast, in pancreas the incorporation into the enzyme was only 5-fold higher than into protein, and in submaxillary gland the incorporation was equivalent. Measured as kallikrein-specific radioactivity relative to total protein radioactivity incorporated in 20 min, kallikrein represents 0.18% of total protein synthesis in the kidney, 0.34% in the pancreas, 0.41% in the colon, but 7.29% in the submaxillary gland. Dietary Na+ restriction increased the relative rate of kallikrein synthesis 1.8-fold in the kidney without a comparable effect in submaxillary gland. In contrast, testosterone increased the relative rate of synthesis 2.3-fold in submaxillary gland, but decreased it in kidney. The data show that endogenous kallikrein synthesis differs markedly in various tissues, and that interventions which are known to change kallikrein content or excretion also change the relative rate of enzyme synthesis.

Immunoreactive tissue kallikrein in human serum

Human urinary kallikrein and an antiserum to it raised in the rabbit were used to detect and quantitate immunoreactive tissue kallikrein in human serum. Both 125I-labeled kallikrein and the unlabeled purified enzyme appear complexed to higher molecular weight entities in serum, but specific binding between radiolabeled enzyme and antiserum was unaffected by the presence of serum or plasma. Parallelism to standard displacement curves was always seen with radioimmunoassay of normal sera as well as with human mixed saliva or pancreatic extracts. Assay sensitivity is 160 pg/ml of serum, or 16 pg per tube. Purified plasma kallikrein or prekallikrein in concentrations up to 10 micrograms/ml showed no displacement. Acetone-kaolin activation of plasma produced the expected 30-fold increase in Tos-Arg-OMe esterase activity but no change in immunoreactive tissue kallikrein levels. Serum concentrations were 3.8 +/- 0.7 (mean +/- SE) ng/ml in 21 normal volunteers, and were similar in patients with Fletcher trait or Hageman factor deficiency. Significantly increased serum concentrations were seen with long-term low dietary sodium intake or acute forms of pancreatitis. Although the relation of this immunoreactive material to any active tissue kallikrein within the circulation remains to be determined, our studies provide a new parameter for the assessment of a system repeatedly suggested to have some role in regulation of vascular resistance.

Kallikrein activation of a high molecular weight atrial peptide

Mammalian atrial extracts contain bioactive peptides that exert profound effects upon renal function and isolated smooth muscle preparations. Gel filtration chromatography of rat atrial extract separates the activity into two peaks having apparent molecular weights of 20,000 to 30,000 and less than 10,000. Mild proteolytic treatment (trypsin 1 U/ml) of the high molecular weight fraction enhances the smooth muscle relaxant activity of this fraction and concomitantly reduces the apparent molecular weight of this fraction to less than 10,000. In this report we show that urinary and submaxillary kallikrein enhances the activity of rat atrial extracts in a similar fashion. Pretreatment of the high molecular weight fraction with either kallikrein (1 microgram/ml) enhances the smooth muscle relaxant activity of this fraction. Similar treatment of the low molecular weight fraction had no effect. The enhancement of the bioactivity of the high molecular weight substance(s) by the kallikreins was abolished by aprotinin but was unaffected by soybean trypsin inhibitor. These results suggest that exogenous addition of tissue kallikrein activates a high molecular weight peptide by limited proteolysis. Analysis of the kallikrein-treated high molecular weight peptide fraction by gel filtration indicates that the biological activity comigrates with the low molecular weight peptides present in the original atrial extract.

Immunoglobulin gene rearrangement as a diagnostic criterion of B-cell lymphoma

We describe the use of the Southern blot hybridization technique to diagnose B-cell lymphoma by detecting clonal immunoglobulin gene rearrangements in lymph node and other biopsy tissues. DNA was isolated from a wide variety of neoplastic and non-neoplastic specimens and analyzed for the presence of rearranged immunoglobulin genes using radiolabeled DNA probes specific for the heavy- and light-chain immunoglobulin constant region genes. Among the specimens examined, clonal immunoglobulin gene rearrangements were found only in biopsy samples of B-cell lymphoma and not in samples containing reactive lymphoid processes or non-B-cell cancers. In lymphomas, the presence of rearrangements for either the kappa or lambda light-chain gene correlated with expression of one or the other of these chains when cellular immunoglobulins could be detected by frozen-section immunophenotyping techniques. The analysis of immunoglobulin gene rearrangements offers several advantages over conventional diagnostic methods for lymphomas, including improved sensitivity in detecting minor populations of neoplastic lymphocytes composing as little as 1% of the total cell population. In addition, clonal immunoglobulin gene rearrangements are demonstrable in a subset of lymphomas that lack detectable surface or cytoplasmic immunoglobulin, thus offering positive evidence for both malignancy and the B-cell origin of these tumors. Our studies indicate that detection of immunoglobulin gene rearrangements is a valuable method for diagnosis and classification of various lymphoproliferative disorders that are difficult to evaluate histologically or that lack distinctive antigenic markers.

Measurement of the Rat Urinary Plasminogen Activator (Esterase A) by Direct Radioimmunoassay in Urine and Tissue

Rat urinary esterase A, a plasminogen activator with kininogenase activity, was recently purified and characterized (J. Chao (1983) J. Biol. Chem. 258, 4434-4439). A sensitive radioimmunoassay for esterase A has been developed. This assay uses a rabbit antiserum in a final dilution of 1:160 000 and the purified enzyme was labelled with 125I using a lactoperoxidase method. It detects 80 pg of immunoreactive material per tube. This antiserum has some cross-reactivity with rat urinary kallikrein (approximately 5%) but a previously characterized tissue kallikrein antiserum has negligible cross-reactivity with the urinary esterase A in the assays. Therefore, kallikrein levels are measured simultaneously in all samples to obtain accurate levels of immunoreactive esterase A. Dilutions of urine or tissue homogenates showed complete parallelism with esterase A standard curves. No cross-reactivity with dog, human or monkey urine was seen. The recovery of esterase A from rat urine was 99.7 +/- 3.5%. Intra- and between-assay errors were 6.5 and 11.2%, respectively. Immunoreactive esterase A was measured and compared with kallikrein levels in rat urine, kidney, pancreas, submandibular gland, descending colon and ileum. The urinary esterase A excretion rate was reduced significantly in rats on a high sodium, compared with a low sodium diet, but not significantly increased above control by the latter. Nonetheless, a significant correlation between urinary kallikrein and esterase A excretion rate was present. This radioimmunoassay can now be used to measure esterase A levels in urine and tissue as questions have arisen about its regulation and functional significance.

Identification of tissue kallikrein in brain and in the cell-free translation product encoded by brain mRNA

A monoclonal antibody against purified rat urinary kallikrein was coupled to agarose and used to isolate kallikrein from rat brain. The purified enzyme has N alpha-tosyl-L-arginine methyl esterase activity with a pH optimum at 9.0, kinin-releasing activity from a purified low molecular weight kininogen, and a parallelism with standard curves of rat urinary kallikrein in a direct radioimmunoassay. Brain kallikrein is inhibited by a series of tissue kallikrein inhibitors with IC50 values similar to those for urinary kallikrein. The purified brain enzyme was labeled with [14C]diisopropylphosphorofluoridate and visualized by fluorography on a sodium dodecyl sulfate-polyacrylamide gel. Electrophoretic mobility of the enzyme was closely similar to that of urinary kallikrein with estimated Mr of approximately 38,000. With Western blot analyses using a rabbit anti-kallikrein antibody, both brain and urinary kallikrein were visualized at identical positions by immunoperoxidase staining and by autoradiography with 125I-protein A binding. Brain mRNA was used to direct cell-free protein synthesis in wheat germ and rabbit reticulocyte lysate systems. [35S]Methionine-labeled kallikrein was identified by fluorography of sodium dodecyl sulfate-polyacrylamide gels after the translation products were subject to immunoprecipitation with affinity-purified kallikrein antibody. Collectively, the data show that tissue kallikrein exists in brain and can be synthesized by brain mRNA.

Differential effects of testosterone, thyroxine, and cortisol on rat submandibular gland versus renal kallikrein

The effects of 17 alpha-methyltestosterone (T alpha), T4, or cortisol (F) on tissue kallikrein in the rat submandibular gland and renal cortex were measured. Castrated male or normal female Sprague-Dawley rats were treated with T alpha or T4 for 2 weeks. In addition, F, T alpha, or T4 was given to adrenalectomized female rats for 2 weeks. In the submandibular glands of male rats, castration resulted in a significant reduction of both kallikrein-like alpha-N-tosyl-L-arginine methyl ester (Tos-Arg-OMe) esterase activity and immunoreactive kallikrein content. Treatment with T alpha or administration of T4 significantly increased Tos-Arg-OMe esterase activity and immunoreactive kallikrein over that in the castrated rats receiving vehicle. Both the Tos-Arg-OMe esterase activity and kallikrein content of the submandibular glands of normal female rats were increased significantly by T alpha or T4. However, T alpha or T4 either significantly reduced or had no effect on renal Tos-Arg-OMe esterase activity or kallikrein content in castrated male or normal female rats. Adrenalectomy had no effect on submandibular gland Tos-Arg-OMe esterase activity and kallikrein content in the female rat, but F or T alpha significantly increased submandibular gland Tos-Arg-OMe esterase activity and kallikrein content. These adrenalectomized female rats showed a marked increase in renal cortical Tos-Arg-OMe esterase activity and kallikrein content, and F, T alpha, or T4 markedly decreased both esterase activity and immunoreactivity. These data show that T alpha, T4, and F modulate both kallikrein-like activity and quantity, but in a generally opposite way in the rat submandibular gland vs. the kidney.

Inhibitory effects of sodium and other monovalent cations on purified versus membrane-bound kallikrein

Glandular kallikrein is a serine proteinase implicated in epithelial ion transport processes. The present studies show that the enzymatic activities (alpha-N-tosyl-L-arginine methyl ester esterase and kininogenase) and the immunoreactivities of rat and human urinary kallikreins are inhibited by monovalent cations. The degree of inhibition, which exceeds 80% with physiological concentrations of cations, is dependent on temperature and preincubation time. The inhibitory effects are reversed when ions are removed via gel filtration. Bovine serum albumin or polyethylene glycol attenuate cationic inhibition, but sucrose or mannitol do not. Detergents, including deoxycholate, 3-[(3-cholamidopropyl)dimethylammonio]-1-propane sulfonate, Triton X-100, and Lubrol PX also attenuate cationic inhibition of enzymatic activity or immunoreactivity. Membrane-bound kallikrein of renal cortical microsomal fractions or detergent-treated purified kallikrein lose less than 30% of their activity, even in the presence of 200 mM cation. These results show that both catalytic activity and immunoreactivity of purified versus membrane-bound kallikreins are affected, but to a different extent, by cations. The data suggest that monovalent cations may play a role in the regulation of soluble versus membrane-bound kallikrein activity.