Kallikreinlike activity in perfusates and urine of isolated rat kidneys

VARIATIONS IN KALLIKREIN-LIKE ESTERASE ACTIVITY IN DIFFERENT SEGMENTS OF THE RAT NEPHRON DURING SALT-LOAD AND SALT-DEPLETION

Histochemical changes in kallikrein-like activity in the rat nephron induced by chronic salt-load or salt-depletion were investigated semiquantitatively, using a synthetic substrate for kallikrein, pro-phe-arg-naphthylester. The location of the changes in the different segments of the nephron was established by comparison with neighbouring freeze-dried sections, where the various structures of the tubular segments were identified. The enzyme activity was graded semiquantitatively and the percentage of tubular segments possessing enzyme activity was recorded. In salt-loaded rats, the enzyme activity in the deep half of the renal cortex was decreased in the first and second segments of the proximal tubule as well as in the third segment in the cortex. In salt-depleted rats, the enzyme activity in the deep half of the renal cortex was also decreased in the first segment of the proximal tubule as well as in the third segment in the cortex. In contrast, the enzyme activity in the second segment of the proximal tubule was increased in the superficial cortex as well as in the deep cortex. Furthermore, in the salt-depleted rats the enzyme activity was decreased in the cortical part of the ascending thick limb of Henle, but increased in the medullary part. In the superficial part of the cortex, the enzyme activity was decreased in the distal convoluted tubule. In the kidneys from both salt-loaded and salt-depleted rats, the differences in enzyme activity between zones--such as found in the normal kidney--disappeared in the case of the first and second segments of the proximal tubule. However, in the other segments of the nephron, the zonal differences were preserved in both experimental conditions.

Human tissue kallikrein attenuates hypertension and secretes into circulation and urine after intramuscular gene delivery in hypertensive rats

Systemic delivery of the human tissue kallikrein transgene has been shown to markedly delay the increase of blood pressure in hypertensive rat models. To demonstrate potential hypotensive effects of kallikrein via local delivery, adenovirus carrying the human tissue kallikrein gene was inoculated into quadriceps of spontaneously hypertensive rats (SHR). A single intramuscular injection of the kallikrein gene caused a significant delay of blood pressure increase for 5 weeks. The expression of human tissue kallikrein and its mRNA was identified solely in injected muscle. Immunoreactive human tissue kallikrein was detected in the muscle as well as in the circulation and urine of adult and newborn rats. Urinary kinin and cGMP levels increased significantly in rats receiving kallikrein gene delivery as compared with rats receiving control virus containing the LacZ gene. The detection of human tissue kallikrein in rat urine after local gene delivery into the muscle provides direct evidence that circulatory kallikrein can be secreted into the urine. These findings indicated that a continuous supply of human tissue kallikrein in the circulation is sufficient to reduce blood pressure and kallikrein gene delivery via the intramuscular route may have significant implications in therapeutic applications.

Expression of human tissue kallikrein in rat salivary glands and its secretion into circulation following adenovirus-mediated gene transfer

Replication-deficient adenovirus Ad.CMV-cHK, expressing human tissue kallikrein under the control of the cytomegalovirus enhancer/promoter, was introduced into rat salivary glands via a direct intracapsular injection. A single injection of Ad.CMV-cHK at a dose of 4 x 10(9) pfu resulted in a sustained expression of human tissue kallikrein in rat salivary glands. The level of immunoreactive human tissue kallikrein in rat sera was the highest at 1 day post gene delivery when both salivary glands were injected and decreased in a time-dependent manner after gene delivery. Human tissue kallikrein levels in sera increased concomitantly with the amount of adenovirus used in direct salivary injection. The detection of human tissue kallikrein in sera after gene delivery into salivary glands provided direct evidence indicating that rat salivary glands secrete locally synthesized human tissue kallikrein to the systemic circulation. The direct injection of salivary glands with replication-deficient adenovirus could provide a systemic route for gene delivery for studying salivary gland function and development. Targeted gene delivery to the salivary gland may provide the means to express therapeutic proteins in saliva and the systemic circulation.

ATP-diphosphohydrolase activity in rat renal microvillar membranes and vascular tissue

Ecto-nucleotidases may have a role in the regulation of purinoceptor-mediated responses. ATP-diphosphohydrolase or apyrase has been described as an ecto-nucleotidase, which is characterized by a low specificity for its substrates and bivalent cations. The aim of this work was to demonstrate the presence of apyrase as an ecto-enzyme in the rat kidney. ATPase-ADPase activities of the renal microvillar membrane preparation, which correspond to "right side out' membranes, were characterized. The detection of ATP-diphosphohydrolase in the renal vasculature was done through perfusion of isolated rat kidney. ATPase-ADPase activities of the microvillar membrane preparation and apyrase share similar kinetic properties. These include: low substrate and bivalent metal specificities and insensitivity towards inhibitors like: oligomycin, ouabain, verapamil, levamisole and Ap5A. The M(r) or native ATPase and ADPase activities was determined by the 60Co irradiation-inactivation technique being around 65 kDa for both hydrolytic activities. Immunowestern blot analysis also supports the presence of apyrase in microvilli. Perfusion of isolated rat kidney with ATP and ADP, in the presence or absence of different inhibitors or apyrase antibodies indicated the existence of this enzyme in the vascular endothelium. The identification of ATP-diphosphohydrolase as an ecto-enzyme both in microvilli and vasculature support the proposal that the enzyme may have an important role in the extracellular metabolism of nucleotides.

Increased urinary excretion of thromboxane B2 and 2,3-dinor-TxB2 in cyclosporin A nephrotoxicity

Cyclosporin A (CsA) administration to rats is associated with a selective increase in urinary excretion of immunoreactive thromboxane B2 (i-TxB2), the stable breakdown product of TxA2. The exaggerated synthesis of TxA2 may play a role in the reduction of glomerular filtration rate (GFR) observed both in animals and humans undergoing CsA treatment. The present study was designed to get further insight into the origin of the abnormal i-TxB2 urinary excretion. Rats given orally CsA (50 mg/kg/day) for 30 days had a significant increase in the urinary excretion of both 2,3-dinor-TxB2 and TxB2 measured by technique of capillary column gas chromatography-negative ion chemical ionization mass spectrometry (HRGC-NICIMS). Urinary TxB2 is more likely to reflect the renal synthesis of the parent compound, whereas 2,3-dinor-TxB2 is considered to reflect the amount of TxB2 formed in the circulation. Experiments in isolated perfused kidney (IPK) taken from animals given CsA for 30 days showed a lower percentage increase in urinary TxB2 over vehicle treated animals. Moreover in IPK the ratio 2,3-dinor-TxB2/TxB2 was lower than in vivo. The amount of i-TxB2 detectable in serum of animals given CsA was not different from that of control animals. In contrast, isolated glomeruli taken from rats given CsA had an increase in their TxA2 synthesis measured as i-TxB2 in the supernatants. Ultrastructural studies on kidney specimens from animals given CsA showed a focal glomerular endothelial damage together with a marked infiltration of blood borne cells of monocyte-macrophage type in the glomerular tuft. In contrast, kidney specimens taken from IPK preparations were devoid of inflammatory cells. In vitro CsA did not interfere with platelet arachidonic acid (AA) metabolism as shown by a normal i-TxB2 generation in vitro by rat platelet-rich plasma (PRP) exposed to CsA and then challenged with AA or ADP. Similarly isolated glomeruli and isolated proximal tubules from normal rats when challenged with CsA in vitro converted AA into TxA2 normally. It is suggested that the cause of the increased urinary excretion of 2,3-dinor-TxB2 is the consequence of intrarenal platelet and macrophage activation, probably triggered by the endothelial damage. The parallel increase in the urinary excretion of unmetabolized TxB2 is likely to reflect a concomitant activation of resident renal cell AA metabolism induced by CsA.

Micropuncture localization of kallikrein secretion in the rat nephron

We have used free-flow micropuncture to study the tubular locus at which kallikrein enters the urine. Kallikrein was measured by a newly developed, very sensitive assay for kininogenase activity; active kallikrein was measured directly by this assay and total kallikrein after activation of inactive kallikrein. Kallikrein was readily detected in all of 17, late distal tubular fluid-samples. In contrast, kallikrein was too low to detect in 15 of 17 proximal or in 11 of 14 early distal tubular fluid samples. Calculations indicate that less than 10% of urinary kallikrein could have derived from filtration or from proximal secretion of kallikrein. We conclude that urinary kallikrein enters the urine via secretion in the distal tubule. Filtration or proximal secretion of kallikrein does not contribute significantly to urinary kallikrein excretion.

Relevance of plasma, glandular and urinary kallikrein in renal hypertrophy in streptozotocin-diabetic rats

The relevance of plasma, glandular and renal kallikrein as an intrarenal hemodynamic regulator, in renal hypertrophy, in 1-5 weeks streptozotocin diabetic rats has been investigated. The fasting plasma glandular kallikrein level significantly decreased with increasing duration of diabetes (p less than 0.05). Glandular kallikrein correlated negatively with kidney weight (r = 0.76, p = 0.05). The 24 hour urinary kallikrein excretion significantly increased with increasing duration of diabetes (p less than 0.05), but this level was not correlated with glucose level, nor with kidney weight. Aprotinin (a kallikrein inhibitor) injected (10 X 10(3) KIU/kg) twice daily for 2 weeks in diabetic rats, significantly decreased plasma glucose levels by 28%, 24 hour urinary kallikrein by 37% (p less than 0.05) and kidney weight by 6%. These results suggest that plasma, glandular and renal kallikrein did not play an important role in the renal hypertrophy observed in streptozotocin diabetic rats.

Urinary kallikrein excretion during inhibition of endogenous angiotensin II in the pig

This study was performed to assess the possible contribution of endogenous angiotensin II (AII) to the regulation of urinary kallikrein excretion. The AII antagonist saralasin or the saline vehicle was infused into the aorta above the renal arteries of pigs under halothane-O2/N2O anaesthesia. Systemic and renal functional parameters were followed for 140 min and during stimulation of the reninangiotensin system by haemorrhage. Urinary kallikrein excretion, determined as kininogenase activity, was increased immediately upon both initiation and termination of the 2 h saralasin infusion into pigs not subjected to haemorrhage. Renal cortical blood flow (RCBF) was maintained, in both saline and saralasin-treated animals at blood pressures as low as 70 mm Hg, while glomerular filtration rate was dissociated during saralasin infusion. As long as RCBF was maintained, urinary kallikrein excretion rate was elevated during the progressive hypotension in both saline and saralasin-treated animals. These findings confirm a close relationship between the maintenance of RCBF and increased activity of the kallikrein-kinin system whether or not AII is antagonized, and indicate that during haemorrhage the kallikrein-kinin system is stimulated by a mechanism not involving AII.

Immunocytochemical localization of renin and kallikrein in the rat renal cortex

Immunocytochemical studies in the past, using alternate serial sections to localize individual antigens, concluded that there was no close relationship between renin- and kallikrein-containing structures in the rat kidney. We have investigated this relationship by simultaneously localizing renin and kallikrein in the same section using immunoperoxidase with two different chromogens. Analysis of serial kidney sections from three rats indicated that kallikrein-containing late distal tubular cells corresponded in their distribution to connecting tubule cells. They were observed in the proximity (less than 3 micrograms) of renin-containing JG cells in 66.6% of the superficial (N = 30), 46.6% of the midcortical (N = 15) and 26.7% of the juxtamedullary (N = 15) afferent arterioles surveyed. When traced through serial sections, 90% of the afferent arterioles from superficial glomeruli (N = 30), 86.7% of the afferent arterioles from midcortical glomeruli (N = 15) and 73.3% of those from juxtamedullary glomeruli (N = 15) came within 3 micrograms of a late distal tubule showing some kallikrein-positive cells. These cells were adjacent to the afferent arteriole in 67 to 80% of the arterioles surveyed. This spatial relationship suggests an anatomical basis for a possible interaction between the afferent arteriole, containing renin-positive JG cells, and kallikrein-positive late distal tubular cells.

Renal kallikrein in diabetic patients with hypertension accompanied by nephropathy

We measured the 24-h excretion of urinary kallikrein in 27 patients with Type 2 (non-insulin-dependent) diabetes and in 10 normal control subjects. Mean (+/- SD) kallikrein excretion in diabetic patients with nephropathy (6.2 +/- 2.4 naphthyl units (NU)/day, n = 13) was significantly lower than in control subjects (12.8 +/- 3.4 NU/day, p less than 0.01) and in diabetic patients without nephropathy (9.4 +/- 3.4 NU/day, n = 14, p less than 0.05). Kallikrein excretion in hypertensive diabetic patients with nephropathy (5.1 +/- 1.6 NU/day, n = 8) was significantly lower (p less than 0.05) than in normotensive patients with nephropathy (8.3 +/- 2.1 NU/day, n = 5). There were no significant differences in kallikrein excretion rate (24-h excretion of urinary kallikrein/24-h creatinine clearance) among control subjects (9.9 +/- 4.3 NU/ml), diabetic patients with (9.0 +/- 3.2 NU/ml) and without (9.3 +/- 3.5 NU/ml) nephropathy. However, kallikrein excretion rate in hypertensive diabetic patients with nephropathy (7.7 +/- 3.3 NU/ml) was significantly lower (p less than 0.05) than in normotensive diabetic patients with nephropathy (11.8 +/- 2.0 NU/ml, n = 10). Respective basal and post-stimulated (with intravenous furosemide 40 mg plus 60 min ambulation) plasma aldosterone concentrations measured in control subjects and in hypertensive diabetic patients with nephropathy were similar and increased to the same extent in the 2 groups (5.5 +/- 3.2 versus 5.3 +/- 3.2 and 9.3 +/- 2.6 versus 10.5 +/- 3.4 ng/ml), although the respective plasma renin activity tended to be lower in diabetic patients than in control subjects (0.7 +/- 0.6 versus 1.3 +/- 0.9 and 1.8 +/- 1.8 versus 3.0 +/- 2.6 ng-1 . ml-1 . h-1).(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma half-life and organ uptake ratio of radiolabeled glandular kallikrein in control and nephrectomized rats

The purified rat urinary kallikrein was radiolabeled by lactoperoxidase method and by chloramine T method. Plasma half-life of radiolabeled kallikrein was 5.06 +/- 0.59 (n = 5) min in control rats and 5.24 +/- 0.42 (n = 5) min in nephrectomized rats. There was no difference between two groups. From autoradiogram, main metabolic organs of radiolabeled kallikrein were liver, kidney and spleen. Total uptake of radiolabeled kallikrein in ech organ was the highest in liver (73.2%). The uptake per g tissue of radiolabeled kallikrein in each organ was high in liver (33.0%), kidney (31.4%) and spleen (21.1%). These results suggest that the active kallikrein is metabolized mainly in the liver, and kidney is not so an important organ to metabolize or to eliminate the active kallikrein in plasma. In order to clarify the mode of existence of active kallikrein in plasma, the following experiment was done by using disc gel electrophoresis. Radioactive profile of radiolabeled kallikrein showed one peak (Rf = 1.0), but radiolabeled kallikrein mixed with rat plasma showed two peaks, that is small peak (Rf = 1.0), and main peak (RF = 0.5). The most of radiolabeled kallikrein was bound to plasma protein and only five per cent was in free form. Furthermore, the binding of radiolabeled kallikrein to plasma protein was interfered by the addition of active kallikrein. These results suggest the possibility of existence of kallikrein binding protein in plasma.

Urinary kallikrein activity in pregnant hypertensive rats

Goldblatt one-kidney one-clip (G1K-1C) hypertensive rats were studied to determine the changes of blood pressure (BP) and urinary kallikrein (UK) excretion throughout pregnancy. Uninephrectomized rats (Unx) were used as controls. Both groups showed a significant decrease in BP on day 21 of pregnancy, although G1K-1C rats had higher values. UK activity was markedly stimulated in both groups, reaching its highest level on day 21. This increment in UK was due to greater delivery and/or synthesis of the enzyme, since no change was observed in the active fraction. We postulate that the highly activated kallikrein-kinin system might be contributing to the hypotensive effect of pregnancy.

Purification of inactive kallikrein from rat urine

An inactive kallikrein was purified from rat urine, and some of the properties of this enzyme were examined, in comparison with those of rat urinary kallikrein (RUK). The purified inactive kallikrein reacted with the antiserum against RUK and migrated slightly more slowly than RUK, on the immunoelectrophoresis. The molecular weights of the inactive kallikrein and RUK were estimated to be 44,000 and 38,000 by gel filtration, respectively. These results indicate that the rat urinary inactive kallikrein is immunologically identical with RUK, but this inactive enzyme has biochemical properties different from those of RUK, with respect to molecular weight and electrophoretical mobility.

Subcellular localization of renal kallikrein by ultrastructural immunocytochemistry

The subcellular distribution of immunoreactive kallikrein was described in the rat nephron using ultrastructural immunocytochemistry. The renal tissue was fixed with a mixture of buffered picric acid-paraformaldehyde-glutaraldehyde and immunostained with the peroxidase-antiperoxidase method for the electron microscope with the following steps: antikallikrein antiserum, anti-IgG serum, peroxidase-antiperoxidase complex, 3-3' diaminobenzidine-H2O2, and post-staining with osmium tetroxide. Preabsorption of the primary antiserum with purified rat urinary kallikrein and substitution with normal serum were used as controls. As we have described previously, kallikrein was present exclusively in the connecting tubule cell of the distal nephron. Subcellularly, kallikrein was distributed in luminal membranes, basal membranes, rough endoplasmic reticulum, Golgi apparatus, and vesicles. The immunoreactive vesicles were present in the proximity of the Golgi apparatus and in the cytoplasm in the way between the Golgi and the luminal and basal plasma membranes. No immunostaining was observed in other subcellular components of the connecting tubule cell or in the other type of cell. With the description of kallikrein in subcellular organelles involved in the synthesis, processing, and transport of glycoproteins, we have advanced an hypothetical intracellular processing pathway for renal kallikrein.

Kallikrein excretion in renal transplant recipients and in uninephrectomized donors

The rate of tissue kallikrein (EC 3.4.21.35) excretion into the urine has been examined with an active site-specific radioimmunoassay for kallikrein in renal transplant recipients, in post-uninephrectomy kidney donors, and in a normal control population. Normal individuals on uncontrolled diets excreted 96.88 +/- 7.00 (SEM) micrograms of active kallikrein/24 hr and 113.68 +/- 8.39 micrograms of total kallikrein/24 hr, as determined after trypsin treatment of urine samples. Uninephrectomized donors secreted significantly less (P less than 0.05) active (44.99 +/- 6.39 micrograms/24 hr) and total (73.59 +/- 11.95 micrograms/24 hr) kallikrein than either the entire normal population or an age-matched subpopulation. Recipients with good renal function who had received kidneys 2 to 13 years prior to kallikrein assay excreted less (P less than 0.05) active (13.21 +/- 2.50 micrograms/24 hr) and total (18.69 +/- 3.65 micrograms/24 hr) kallikrein than either normal or uninephrectomized populations. Similar values for active (11.05 +/- 1.56 micrograms/24 hr) and total (17.60 +/- 1.96 micrograms/24 hr) kallikrein were seen in patients who had received kidneys within 6 months of assay. Thus, kallikrein excretion in kidney recipients remains significantly lower than in uninephrectomized donors. As compared to normal individuals, the reduced kallikrein excretion in post-uninephrectomized kidney donors and in renal allograft recipients suggests that renal kallikrein excretion may reflect functional distal tubular mass.

Activation of human and rabbit prokallikrein by serine and metalloproteases

Human and rabbit kidney and urine contain an inactive form of kallikrein. Studies on the mRNA sequence suggested that the active form of the enzyme and the propeptide are linked by a peptide bond between a basic and hydrophobic amino acid. We studied the activation of prokallikrein by serine proteases and a neutral metalloproteinase, thermolysin, because serine proteases cleave the peptide chain after a basic amino acid and thermolysin before a hydrophobic amino acid. The activity of kallikrein was measured by RIA and with a fluorogenic peptide substrate. Trypsin was used as a standard reference activator. We found that human plasmin and plasminogen, activated by urokinase, activate prokallikrein. Pronase coupled to Sepharose also enhanced the activity of the renal kallikrein zymogen. On a molar basis, thermolysin was a more effective activator of prokallikrein than trypsin. The activation by thermolysin was blocked by the inhibitor phosphoramidon, but not by DFP or SBTI. These experiments indicate that, in addition to serine proteases, neutral metalloproteases of tissues may activate prokallikrein.

Effect of the protease inhibitor aprotinin on renal hemodynamics in the pig

Aprotinin, the serine protease inhibitor that also inhibits glandular (urinary) kallikrein, or vehicle was infused into the aorta above the renal arteries of anesthetized pigs. Renal hemodynamic and functional parameters were followed over time and during hemorrhagic hypotension. Both renal cortical blood flow and glomerular filtration rate were maintained in vehicle-treated animals at mean arterial pressures as low as 70 mm Hg. As long as renal cortical blood flow and glomerular filtration rate were maintained during the progressive hypotension, urinary excretion rate of kallikrein (as defined by kinin-generating activity) was increased. In contrast, all aprotinin-treated animals had a decreased excretion rate, and the renal cortical blood flow declined with the mean arterial pressure during hemorrhage. The pattern of glomerular filtration rate and plasma renin activity was comparable in both aprotinin-treated and vehicle-treated hemorrhaged animals. Our findings suggest that the endogenous renal kallikrein-kinin system is required for functional renal vasodilatation to maintain renal cortical blood flow during hemorrhage and is therefore directly or indirectly responsible for adjustment of preglomerular resistance.

Effect of atrial natriuretic factor [ANF (Arg 101--Tyr 126)] on kallikrein and cyclic GMP in the renovascular hypertensive rat

The intravenous injection of an ED50 natriuretic dose (1 microgram) of synthetic ANF decreases blood pressure by 61 +/- 6 mmHg in 2-K, 1-C, and of 45 +/- 6 mmHg in 1-K, 1-C hypertensive rats, which was positively correlated with its initial level only in the 2-K, 1-C group. The hypotensive response lasted longer in the latter (greater than 40 min) than in normotensive sham-operated rats. No difference in duration was seen between 1-K, 1-C hypertensive and its uninephrectomized normotensive controls. The diuretic response to ANF was higher in 2-K, 1-C rats. No hematocrit changes were observed in any group. ANF induced a rise in urinary kallikrein in all groups but the 1-K, 1-C. Urinary kallikrein excretion was positively correlated with natriuresis in normotensive but not in hypertensive groups. ANF induced an increase in urinary cGMP excretion in all groups but the 1-K, 1-C, and an increase in plasma cGMP in the normotensive sham-operated animals. Our results suggest that the fall in blood pressure induced by synthetic ANF could be due to vasodilatation, a drop in cardiac output cannot, however, be eliminated. Whether the hypotensive effect of ANF is mediated by cGMP remains to be demonstrated.

Isolation and characterization of rat plasma glandular kallikrein

A method has been developed to purify glandular kallikrein present in rat plasma by using Sepharose-Aprotinin affinity chromatography and elution of the enzyme with p-aminobenzamidine. The isolated enzyme liberated kinins from kininogen II of low molecular weight (sp. act. 14 ng kinins/min X mg) and p-nitroaniline (pNA) from the substrate S-2266 (sp. act. 1.23 nmoles pNA/min X mg); it was inhibited by aprotinin, benzamidine and rat urinary antikallikrein antibody but not by ovomucoid. In polyacrylamide gel electrophoresis, the enzymatic activities of the preparation were associated with two light protein bands of molecular weights equal to that of urinary kallikrein (35,000 daltons). Using this method, the recovery of [125I]kallikrein added to the plasma was 82-88%. The concentration of the enzyme in normal rat plasma was equivalent to 6.1 +/- 2.1 (S.D.) ng kallikrein/ml. The mean value found in nephrectomized rats was 20.0 +/- 6.3 (S.D.) ng kallikrein/ml. This increment was highly significant (P less than 0.001). Our results confirm the presence of glandular kallikrein in plasma which had been detected by other methods; they also demonstrate that the material purified from plasma is enzymatically active, suggesting that kallikrein may play a biological role in the control of blood circulation.

Increased urinary kallikrein-like activity during ADH-induced hyponatremia in rats

The urinary kallikrein system was studied during hyponatremia associated with water and vasopressin administration in rats. Two groups of animals were studied. In the experimental group (n = 5), vasopressin (0.4 U/day) was injected intramuscularly for 7 days, and water (15%-20% body weight per day) was given via a stomach tube. The control group (n = 6) received only vasopressin. In the experimental group, plasma sodium concentration (PNa) decreased from 143.2 +/- 0.5 to 130.8 +/- 1.8 (m +/- SEM) mmol/liter (5th day, p less than 0.01) along with plasma osmolality. Urinary kallikrein-like activities (UkaV) increased from 99.1 +/- 7.5 to 172.6 +/- 23.5 mumol X min/day (100 g body weight) (5th day, p less than 0.05; 6th day, p less than 0.05; and 7th day, p less than 0.05) after the administration of vasopressin. Uric acid clearance (Cua) increased from 0.153 +/- 0.014 to 0.275 +/- 0.041 ml/min (5th day, p less than 0.05; 7th day, p less than 0.05). No change was observed in urinary aldosterone excretion (UAldV), creatinine clearance, or blood pressure. UkaV correlated with Cua (r = 0.81, p less than 0.01) and with the degree of change of PNa (r = --0.79, p less than 0.01), respectively. In the control group, no change was observed in the above parameters. A significant relationship between UkaV and fractional Na clearance (r = 0.60, p less than 0.01) was observed. We conclude that the urinary kallikrein system in rats may be stimulated during hyponatremia when induced by water and vasopressin. This increased activity is probably the result of volume expansion associated with water and vasopressin and may have some relationship to fractional Na clearance in the kidney.

Interactions of lysyl-bradykinin and antidiuretic hormone in the rabbit cortical collecting tubule

Although intrarenal infusions of kinins produce diuresis, it is not clear to what extent this response is due to hemodynamically mediated medullary washout and/or to direct epithelial effects of kinins. Recent evidence has shown that bradykinin binds to collecting tubules in vitro. We therefore examined the interactions of lysyl-bradykinin and antidiuretic hormone (ADH) with respect to hydraulic conductivity (Lp) in the rabbit cortical collecting tubule perfused in vitro. To ensure adequate substrate for prostaglandin synthesis, the bath contained 2.5 microM arachidonic acid. Arachidonic acid produced no change in base-line Lp and had no effect on the subsequent response to a supramaximal dose of ADH (100 microU/ml). Therefore, all subsequent experiments were done in the presence of arachidonic acid. Lysyl-bradykinin (10(-9)M) added to either the lumen or bath had no effect on base-line Lp. Collecting tubules which were exposed for 1 h to bath lysyl-bradykinin (10(-9)M) had a significantly diminished subsequent Lp in response to ADH (P less than 0.02). In tubules exposed to bath lysyl-bradykinin plus indomethacin (5 microM), the subsequent ADH response was normal. Lysyl-bradykinin (10(-9)M) added to the lumen had no effect on subsequent ADH response. We conclude that lysyl-bradykinin from the basolateral side inhibits the hydroosmotic response of the cortical collecting tubule to ADH, and that this inhibition is probably prostaglandin-mediated. Lysyl-bradykinin does not affect water flow from the luminal surface. These data indicate that the diuresis seen with kinin infusions may result, at least in part, from a direct epithelial effect. They also suggest a role of the renal kallikrein-kinin system in modulating water transport in vivo.

Kallikrein-kinin and renin-angiotensin systems in rat renal lymph

Rat renal lymph contains 254 +/- 17 ng/ml (means +/- SEM, N = 20) of immunoreactive glandular kallikrein. Like the immunoreactive glandular kallikrein in plasma, it is biologically inactive. Gel filtration of renal lymph reveals profiles for immunoreactive glandular kallikrein, protein, and inhibition of trypsin and kallikrein which resemble those seen for plasma except that high molecular weight plasma components are reduced or missing in renal lymph. In contrast, gel filtration of thoracic lymph reveals immunoreactive glandular kallikrein and protein profiles which are indistinguishable from those seen with plasma. Renin levels are 170-fold higher in renal lymph than in thoracic lymph while angiotensin-converting enzyme levels are only 16% those of thoracic lymph. In keeping with the high renin and low converting enzyme activities, renal lymph contains high levels of angiotensin I. Immunoreactive glandular kallikrein levels in renal lymph, thoracic lymph and plasma do not show the striking differences observed for renin.

Effect of metoprolol on 24-hour urinary excretion of adrenal steroids and kallikrein in patients with essential hypertension

Treatment of fifteen patients with essential hypertension over four weeks using the beta 1-adrenoceptor blocking agent, metoprolol, resulted in a decrease in 24 h urinary excretion of kallikrein and aldosterone along with a decrease in plasma renin activity. There was no significant change in 24 h excretion rates of the free adrenal steroids deoxycorticosterone, 18-OH-deoxycorticosterone, corticosterone, cortisol or 18-OH-corticosterone during treatment, which were not significantly different from excretion rates of normal males, thus excluding inhibitory effects of adrenal steroids on urinary kallikrein activity. A positive correlation was found between plasma renin activity and urinary excretion of kallikrein during the control period and after 2 weeks on metoprolol, supporting the assumption of a preserved link between the renin-angiotensin-aldosterone system and the renal excretion of kallikrein in these patients. The decrease in kallikrein excretion during beta 1-adrenoceptor blockade in patients with essential hypertension may be explained by a reduction in sympathetic tone and by reduced activity of the renin-aldosterone system.

Immunoreactive glandular kallikrein in plasma during alterations of urinary kallikrein excretion

To determine whether maneuvers known to modify immunoreactive urinary kallikrein excretion (iUKK) also alter the concentration of immunoreactive glandular kallikrein (iGKK) in plasma, we measured iGKK in the plasma and urine of rats before, at 1 week, and at 3 weeks after induction of two-kidney, one clip hypertension, low sodium intake, and DOCA-salt hypertension. Glandular kallikrein in plasma and urine was measured by radioimmunoassay. Clipping of a renal artery decreased iUKK from 11.7 +/- 0.5 microgram/24 hr/100 g body weight (BW) to 7.8 +/- 0.5 and 8.2 +/- 0.5 at 1 and 3 weeks after surgery without significantly changing iGKK in plasma. The level of iGKK in the plasma did not correlate significantly with iUKK in the clipped group. Low sodium intake significantly increased iUKK, which rose from 6.6 +/- 0.3 microgram/24 hr/100 g BW to 9.6 +/- 0.5 and 13.9 +/- 0.7 after 1 and 3 weeks. In addition, low sodium intake appeared to increase iGKK in plasma, and a significant positive correlation was observed between iUKK and iGKK in plasma in the group on low sodium diet (r = 0.65, p less than 0.01). DOCA-salt treatment increased iUKK significantly from 10.4 +/- 0.6 microgram/24 hr/100 g BW to 17.1 +/- 1.4 and 22.6 +/- 2.3 at 1 and 3 weeks after. The iGKK in plasma increased from 13.8 +/- 0.5 to 15.4 +/- 0.7 ng/ml (p less than 0.05) at 1 week after the DOCA-salt treatment began, but it returned to pretreatment levels 3 weeks later (14.5 +/- 0.7 ng/ml, n.s.).(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of kallikrein and renin release by the isolated perfused rat kidney

Rat kidneys perfused in vitro released kallikrein in urine, and renin and kallikrein in the perfusate. The kallikrein was characterized by its kininogenase activity and released bradykinin from bovine and dog substrates. Inactive trypsin activatable kallikrein was present in both perfusate and urine. Kallikrein secretion in urine was influenced by changes in perfusion pressure (PP). Raising the PP strikingly increased urinary kallikrein and lowering PP reduced it. Urinary water and electrolyte output were augmented to the same extent by furosemide and mannitol administration as by raising the PP, but neither drug affected kallikrein. Isoproterenol stimulated the release of renin but not kallikrein. Stopping the oxygen supply to the perfusate suppressed kallikrein secretion in urine and renin release in the perfusate. The kidneys released ten times less kallikrein in the perfusate than in urine, and perfusate kallikrein was not influenced by changes in PP. It is concluded that in this model, changes in PP and/or renal blood flow and/or oxygen supply regulate kallikrein secretion in urine, but that this secretion is unaffected by changes in urinary output. We also conclude that kallikrein release in urine and renin release in perfusate are regulated simultaneously by renal hemodynamic changes but are not affected concomitant by beta-adrenergic stimulation or changes in distal urine composition.

Existence of prokallikrein in the kidney. Its biochemical properties compared to three active glandular kallikreins from the kidney, serum, and urine of the rat

Prokallikrein in the kidney was partially purified with immunoaffinity and DEAE Sephadex A-50 column chromatographies, and its biochemical properties were studied in comparison to three active glandular kallikreins purified from kidney, serum, and urine of the rat. The properties of the enzyme obtained by trypsin activation of prokallikrein were identical with those of active glandular kallikreins from the kidney, serum, and urine of the rat. Apparent molecular weights of prokallikrein, trypsin-activated kallikrein, active renal kallikrein, and glandular kallikrein in rat serum were 38,000 and of active urinary kallikrein, 37,000. Prokallikrein fraction was activated only by trypsin, but not by acidification, pepsin, and rat urinary esterase A treatments. Renal kallikrein, purified in the presence of soybean trypsin inhibitor (SBTI), contained 85% prokallikrein, but the enzymic fraction, purified in the absence of SBTI, contained 23% prokallikrein. Prokallikrein contents of urinary kallikrein and glandular kallikrein in rat serum were 16% and 20% respectively. These results suggest that prokallikrein is produced in the kidney and activated easily by a trypsin-like enzyme. Since rat serum contains active glandular kallikrein, kallikrein in the kidney may be secreted not only into the urine, but also into the blood.

Rat pancreatic kallikrein mRNA: nucleotide sequence and amino acid sequence of the encoded preproenzyme

We have cloned via recombinant DNA technology the mRNA sequence for rat pancreatic preprokallikrein. Four cloned overlapping double-stranded cDNAs gave a continuous mRNA sequence of 867 nucleotides beginning within the 5'-noncoding region and extending to the poly(A) tail. The mRNA sequence reveals that pancreatic kallikrein is synthesized as a prezymogen of 265 amino acids, including a proposed secretory prepeptide of 17 amino acids and a proposed activation peptide of 11 amino acids. The activation peptide, although similar in length, is distinct from those of the other classes of pancreatic serine proteases. The amino acid sequence of the predicted active form of the enzyme is closely related to the partial sequences obtained for other kallikrein-like serine proteases including rat submaxillary gland kallikrein, pig pancreatic and submaxillary gland kallikreins, the gamma subunit of mouse nerve growth factor, and rat tonin. Key amino acid residues thought to be involved in the substrate-cleavage specificity of kallikreins are retained. Hybridization analysis showed relatively high levels of kallikrein mRNA in the rat pancreas, submaxillary and parotid glands, spleen, and kidney, indicating the active synthesis of kallikrein in these tissues.

Kallikrein and prekallikrein of the isolated basolateral membrane of rat kidney

A basolateral membrane (BLM) enriched fraction of the homogenized rat kidney contained kallikrein and prekallikrein which differ from urinary kallikrein. Triton X-100 (0.1%) or melittin (10(-7) - 10(-5)M) solubilized the membrane-bound enzyme. Prekallikrein was activated by trypsin and plasmin. Active kallikrein and activated prekallikrein cleaved the chromogenic substrate S-2266 and released bradykinin from kininogen. Aprotinin and antiserum to rat urinary kallikrein inhibited BLM kallikrein. Gel electrophoresis separated activated BLM prekallikrein and kallikrein; prekallikrein even after activation moved slower (Rf = 0.3) in electrophoresis at an alkaline pH than active kallikrein (Rf = 1). Gel filtration resolved BLM kallikrein to two proteins of low (4 X 10(4) M) and high (1.5 X 10(5) M) molecular weight. After isoelectric focusing of the activated BLM fraction, two kallikreins with pIs of 3.9 and 5.3 were obtained. The BLM fraction also contained renin which became active after Triton treatment. Renin activity was not enhanced by trypsin or acid pH indicating that there was no prorenin present. Thus, BLM of rat kidney contains a kallikrein which is different from urinary kallikrein. This kallikrein, when released from basal membrane, may appear in renal lymph and venous effluent.

Effect of dihydralazine on the renal kallikrein-kinin system of the rat

Dihydralazine (0.1 mg/kg), injected intravenously into male Sprague-Dawley rats, caused a decrease in mean arterial blood pressure and an increase in renal plasma flow, while urine volume remained unchanged. Dihydralazine had no effect on kallikrein excretion in the urine and on kallikrein activity in the renal cortex. No correlation was found between renal kallikrein and either renal plasma flow or mean arterial blood pressure. The excretion of kinins in the urine rose markedly after the administration of dihydralazine; no correlation between urinary kinins and urinary or renal kallikrein was observed. Dihydralazine had no influence on the kininogen content of blood-free renal cortex. The enzymatic activity of kininase II in renal cortex was not impaired by dihydralazine. It is suggested that the increased formation of kinins within the kidney could be involved in the vasodilating and blood pressure lowering effect of dihydralazine.

Prekallikrein, kallikrein and renin in membrane fractions of rat kidney

Two different plasma membrane enriched fractions were isolated from the homogenized rat kidney by differential centrifugation in dextran or sucrose. Marker enzymes and morphological studies indicated that one fraction (BLM) was enriched in membrane particles originating from the basolateral membrane of tubular cells, while the other, the PM fraction, contained membrane from the luminal side. Membrane-bound kallikrein and renin were found in both fractions. Kallikrein activity was enhanced by phospholipase A2, melittin and detergents. Renin activity was greatly increased after solubilization by the same agents. In addition to bound kallikrein and renin BLM contained a prekallikrein which was activated by trypsin or plasmin. BLM prekallikrein has a slower electrophoretic mobility and a higher molecular weight than urinary or glandular kallikrein. The basal membrane of tubular cells appears to contain all of the essential enzyme components of the kallikrein and renin systems. Kallikrein of the PM fraction is probably released into the urine, while prekallikrein and kallikrein from basal membrane may be the source of kallikrein in lymph and renal venous effluent. Membrane-bound renin could be a form of renin retained by the kidney.

Urinary kallikrein and plasma renin activity in normal human pregnancy

Urinary kallikrein excretion (UK), plasma renin activity (PRA), and 24-hour urine volume, sodium, and potassium excretion rates were determined sequentially in 16 normal pregnant women. Throughout gestation, UK was significantly elevated as compared to values obtained in 13 control women (1466 +/- 152 vs 375 +/- 90 U/g creatinine). The highest level was observed in Period 2 of gestation, corresponding to Weeks 17 to 24. PRA was also significantly elevated during pregnancy (11.97 +/- 1,35 vs 1.06 +/- 0.90 ng/ml/hr), with the highest level in Period 2. Mean 24-hour urine volume, sodium, and potassium excretion rates were significantly higher during pregnancy. Nor correlation was found between UK and: PRA, urine volume, and sodium and potassium excretions. These findings indicate a consistent activation of the renal-kallikrein-kinin system during pregnancy. We postulate that this vasodilator system might play a role in the maintenance of normotension in pregnancy, counteracting tha effect of the renin-angiotensin-aldosterone system.

Kallikrein and prekallikrein on the basolateral membrane of rat kidney tubules

Basolateral membrane (BLM) enriched fraction was isolated from homogenized rat kidney cortex by differential centrifugation. We also obtained a fraction enriched in plasma membrane (PM). The morphology of the isolated BLM fragments was studied by transmission and freeze fracture electron microscopy. The relative specific activity of Na+-K+-ATPase was enriched 7-fold, while that of marker enzymes for PM, endoplasmic reticulum, and lysosomes was lower than in the crude homogenate. There was a 10-fold difference in the ratios of activities of Na+-k+-ATPase to Mg2+-ATPase in the BLM and in the PM enriched fractions. Kallikrein activity was determined with S-2266 substrate and by radioimmunoassay of kinin released. It was low in the BLM fraction prior to adding detergent, but Triton X-100 increased the activity 12 to 16-fold. Both free trypsin and Sepharose 4B-bound insoluble trypsin increased kallikrein activity 2- to 3-fold in both the membrane-bound and soluble fractions, probably by activating a prekallikrein. The results were interpreted that the kallikrein studied originated from the distal tubular BLM.

Release of activatable kallikrein by isolated rat kidneys

Rat isolated kidneys were perfused for 60 minutes with a modified Krebs-Henseleit bicarbonate solution. Perfusate and urine samples showed kininogenase activity (active kallikrein) which could be enhanced by activation with trypsin (activatable kallikrein). Identification of the kininogenase activity generated by trypsin was made with rat renal kallikrein antiserum, aprotinin, lima bean trypsin inhibitor (LBTI), soybean trypsin inhibitor (SBTI), and ovomucoid. A sample of perfusate was partially purified through DEAD-Sephacel chromatography. Intraarterial injection of this fraction decreased blood pressure in the perfused hind limb of a rat.

Kinins in relation to kallikrein activity, kininogen, electrolytes, aldosterone and catecholamines in urine from normal individuals

The object of the present study was to test the hypothesis that urinary kinin excretion is an indicator of intrarenal kinin formation and to investigate urinary excretion of kinins in relation to natriuresis, kaliuresis, diuresis and urinary aldosterone and catecholamines in normal individuals on a free salt and water intake. In freshly voided urine collected from 24 normal individuals kinin concentration was directly related to kallikrein activity. Kininogen concentration was very low and neither related to kallikrein activity nor to kinin concentration. The excretion rates of kinins and kininogen were unrelated to the time interval between micturitions. In 24 hour urine collections from 50 normal individuals the excretion of kinins was positively correlated to natriuresis, kaliuresis and diuresis and also to dopamine but not to aldosterone, noradrenaline and adrenaline. Kinin excretion was inversely related to age and was lower in women than in men. On the basis of these results it is concluded that urinary kinin excretion reflects intrarenal kinin formation in normal ambulatory individuals and that urinary kinins are formed mainly in the interstitial and vascular space of the kidney. Furthermore, kinins and dopamine seem to play a physiological role in the renal handling of electrolytes and water.

Activation of membrane-bound kallikrein and renin in the kidney

Rat kidney contains membrane-bound renin (EC 3.4.99.19) and kallikrein (EC 3.4.21.8). Kallikrein activity was measured by a spectrophotometric assay and renin by radioimmunoassay. Plasma membrane-bound kallikrein was activated by lysolecithin and by melittin, which was a more potent activator., This activation by mellitin was independent of calcium concentration. Mellitin was, however, a more potent activator of membrane-bound renin in the presence of calcium. Administration of aldosterone to rats for 6 days increased kallikrein activity in the renal homogenate and in the membrane-enriched fractions, whereas renin activity was not affected. It was proposed that kallikrein may also be located on the basal membrane of tubular epithelial cells, where aldosterone can enhance its activity.

Ureteral contractions induced by rat urine in vitro: probable involvement of renal kallikrein

Rat urine, even at a 1:10 final dilution in Tyrode's solution, stimulates contraction of the ureteral musculature in vitro. This effect can be ascribed to the presence of kallikrein or a kallikrein-like enzyme in urine. Isometric contractions of ureters were prevented by previous addition of aprotinin to the organ bath. Urine also lost its activity after inactivation of enzymes by heat or acid treatment.

Intraglandular transport of 125I-glandular kallikrein in the rat submandibular salivary gland

The transport of radiolabelled rat submandibular gland kallikrein was studied after local administration to the resting and activated rat submandibular gland. The iodinated kallikrein was electrophoretically, immunologically, and biologically indistinguishable from the intact enzyme. After intraductal and intraglandular application the radioactivity in venous effluent was quantitated and characterized. As judged by gel-filtration 125I-kallikrein in venous effluent eluted at a position similar to that seen when the iodinated enzyme was mixed with plasma, but earlier than the elution of 125I-kallikrein in buffer. In plasma, therefore, glandular kallikrein is probably bound to macromolecules. The radioactive fractions in venous effluent did not contain free iodine. Maximum concentration of 125I-kallikrein in venous effluent of resting glands was repeatedly reached about 20 min after intraductal administration. Moreover, the ductal epithelium represented the main permeation barrier since after intraglandular application the maximum venous 125I-kallikrein concentration was reached almost immediately. In activated gland (parasympathetic and sympathetic nerve stimulation), the venous 125I-kallikrein concentration was inversely related to glandular blood flow. We conclude that kallikrein present in the duct lumen or in the interstitium is able to reach the circulation, thereby making possible the local generation of plasma-kinins.

The kallikrein-kinin system in essential hypertension

The kallikrein-kinin system is a potent vasodilator system with components in plasma and in exocrine glands, including the kidney. Kinins function as local hormones and exert effects on blood vessels and on water and electrolyte balance. The most frequently studied component of this system, urinary kallikrein, has been shown to respond to changes in sodium-retaining steroid activity and in renal blood flow. Urinary kallikrein is subnormal in patients with either essential or renovascular hypertension and supranormal in patients with primary aldosteronism or Bartter's Syndrome. The changes in the kallikrein-kinin system appear to be secondary to changes in blood pressure or in other vasoactive systems: i.e., kinins appear to attenuate the vasoconstrictor effects of angiotensin and stimulate the vasodilator actions of the prostaglandins. The kallikrein-kinin system is altered in hypertension, however, its role in this disease remains unclear.

[Renal kallikrein-kinin system and control of blood pressure (author's transl)]

Kallikrein excreted with the urine appears to be formed in the kidney. The kallikrein-kinin system in the kidney is localized in the distal nephron from the juxtaglomerular apparatus to the collecting duct. It has been shown that intrarenal infusion of kinins produces an increase in renal blood flow as well as diuresis and natriuresis. Part of the effect of kinins appears to be mediated by the release of prostaglandins. However, the precise role of the renal kallikrein-kinin system in sodium and volume homeostasis and in blood pressure regulation still remains to be determined. Mineralocorticoids as well as the diuretics furosemide, bumetanide and bendroflumethiazide increase, spironolactone decreases kallikrein excretion. Urinary kallikrein has been shown to increase acid-as well as cryoactivation of prorenin in vitro. It is unclear as yet, however, whether the renal kallikrein-kinin system takes part in converting inactive prorenin into active renin in vivo. There are reports on subnormal, normal as well as increased kallikrein excretion in spontaneously hypertensive rats. In rats susceptible to the hypertensive effect of salt a substantially decreased excretion of kallikrein has been observed. Kallikrein excretion has been described to be increased in primary aldosteronism and to be reduced in a proportion of patients with established essential hypertension. In patients with labile hypertension, however, kallikrein excretion appears to be normal suggesting that decreased urinary kallikrein in essential hypertension is a consequence rather than a cause of hypertension. The renal kallikrein-kinin system does not appear to play a primary role in the pathogenesis of hypertension.

N-Chloroacetyl 5-methoxytryptamine (isamide): a selective antagonist of 5-hydroxytryptamine in the rat uterus

Isamide, the N-chloroacetyl derivative of 5-methoxytryptamine, produced a dose-dependent competitive blockade of uterine contractions in vitro induced by 5-HT. The pA2 value for the 5-HT-isamide interaction was 4.42. The blockade was short-lasting and reversible; after recovery, a dose-dependent increase in the uterine sensitivity to 5-HT was found. The blockade proved to be selective to the 5-HT receptor. The simultaneous application of 5-HT plus isamide partially prevented the 5-HT-induced auto blockade phenomenon. In addition, isamide did not affect the contractile responses of the uterus to oxytocin or bradykinin or the contractile effects of the rat vas deferens to adrenaline.