Endoscopic resection as a first therapy for gastric epithelial atypia: is it reasonable?

BACKGROUND AND AIMS

Gastric atypical cell (GAC), an indefinite pathologic finding, often requires repeated biopsy or other diagnostic treatments, such as endoscopic mucosal resection (EMR), endoscopic submucosal dissection (ESD), or operation (OP). The aim of this study was to analyze the initial endoscopic and histologic findings of GAC and to discuss the necessity of EMR/ESD at establishing a correct diagnosis.

METHODS

This retrospective study enrolled 96 patients proven as GAC on index forceps biopsy. ESD (17/96, 17.7%), EMR (5/96, 5.2%), OP (20/96, 20.8%), and other treatment or follow-up (54/96, 56.3%) were performed. We analyzed the initial endoscopic and histologic characteristics of GAC lesions, predictive of neoplasm.

RESULTS

After diagnostic modalities, the final pathologic diagnoses were cancer (36/96, 37.6%), dysplasia (9/96, 9.4%), and non-neoplasm (51/96, 53.0%). In univariate analysis, age [odds ratio (OR) 1.04, 95% confidence interval (CI) 1.01-1.07], lesion size of 10 mm or greater (OR 3.94, 95% CI 1.61-9.61), lesion with depressed type (OR 2.50, 95% CI 1.09-5.72), and presence of H. pylori (OR 2.83, 95% CI 1.11-7.25) were risk factors for neoplasm. In multivariate analysis, lesion size of 10 mm or greater (OR 3.63, 95% CI 1.23-10.66), lesion with depressed type (OR 2.86, 95% CI 1.11-7.38) were independent risk factors for cancer.

CONCLUSION

Considering the neoplastic risk of GAC, which could be missed on biopsy, more comprehensive tissue sampling via EMR/ESD might be necessary to establish a definite diagnosis.

MAD2 Expression in Ovarian Carcinoma: Different Expression Patterns and Levels among Various Types of Ovarian Carcinoma and Its Prognostic Significance in High-Grade Serous Carcinoma

BACKGROUND

Mitotic arrest deficiency protein 2 (MAD2) is a key component of spindle assembly checkpoint function, which mediates cell apoptosis through microtubule kinetics. Aberrant expression of MAD2 is believed to be associated with the development of chromosome instability. MAD2 also has a signihicant role in cellular drug resistance to taxane chemotherapeutic agents.

METHODS

Expression of MAD2 and p53 was investigated using immunohistochemistry in 85 cases of ovarian carcinomas. Clinicopathological data including progression-free survival were analyzed.

RESULTS

A significant (p=.035) association was observed between the grade of serous carcinoma and the expression level of MAD2. While low-grade serous carcinoma showed a low-level expression of MAD2, high-grade serous carcinoma showed a high-level expression of MAD2. We also determined that low-level expression of MAD2 was associated with reduced progression-free survival (PFS) (p=.016) in high-grade serous carcinoma.

CONCLUSIONS

MAD2 expression in ovarian carcinoma is related to the grade of serous carcinoma and PFS of high-grade serous carcinoma. Expression level of MAD2 detected by immunohistochemistry may serve as an indicator in predicting the response of microtubule-interfering chemotherapeutic agents.

Methionine adenosyltransferase I/III deficiency: two Korean compound heterozygous siblings with a novel mutation

Two Korean sisters, one detected during neonatal screening, the other ascertained at age 3 years during family screening, have persistent hypermethioninaemia without elevation of plasma tyrosine or severe liver disease. Plasma total homocysteine (tHcy) is mildly elevated, but not so markedly as to establish a diagnosis of homocystinuria due to cystathionine beta-synthase (CBS) deficiency. CBS deficiency was ruled out by the presence of slightly elevated concentrations of plasma cystathionine. Although the plasma concentrations of methionine were markedly elevated, plasma S-adenosylmethionine (AdoMet) was not. This pattern of metabolic abnormalities suggested that the patients have deficient activity of methionine adenosyltransferase (MAT) in their livers (MAT I/III deficiency). Molecular genetic studies demonstrate that each patient is a compound heterozygote for two mutations in MAT1A, the gene that encodes the catalytic subunit that composes MAT I and MAT III: a previously known inactivating G378S point mutation, and a novel W387X truncating mutation. W387X mutant protein, expressed in E. coli and purified, has about 75% of wild-type activity. Negative subunit interaction between the mutant subunits is suggested to explain the hypermethioninaemia of these sisters. They have had normal growth and development and have no mental retardation, neurological abnormalities, or other clinical problems. They are the first individuals of Korean descent proven to have MAT I/III deficiency.

Comparison of effects of angiotensin peptides in the regulation of clitoral cavernosum smooth muscle tone

The isometric tension measurement and in vitro autoradiography were used in clitoral cavernosum smooth muscle (CSM). Angiotensin ANG III, ANG IV, ANG II and ANG I induced contractions in clitoral CSM strips. ANG III and ANG I- induced contraction was five times less active than ANG II, whereas ANG IV-induced contraction was 1181-fold less potent than ANG II. Contractile responses to ANG III, ANG IV, ANG II and ANG I were significantly inhibited by type 1 ANG II (AT 1) receptor antagonist Dup 753 but not by type 2 ANG II (AT2) receptor antagonist PD 123,319. Pre-treatment with Nomega-nitro-L-arginine methyl ester, nitric oxide (NO) synthase inhibitor accentuated force of contraction induced by ANG III, ANG IV and ANG II. Amastatin, an aminopeptidase inhibitor enhanced ANG III- and ANG IV-induced contractions. Specific binding sites for 125I-ANG II were found in the clitoral CSM. Specific binding of 125I-ANG II was displaced by unlabeled ANG peptides. This study suggests that the contractile responses to all four peptides of the ANG family are mediated via AT1 receptors but not AT2 receptors. Further, the rank order of potency of contraction was as follows, ANG II> ANG I>ANG III>ANG IV. It is also suggested that peptides of the ANG family have a cross-talk with the NO system and aminopeptidase is involved in the modulation of the tone of clitoral CSM by ANG III and ANG IV.

Nociceptin/orphanin FQ increases ANP secretion in neonatal cardiac myocytes

Nociceptin (N/OFQ) is a novel heptadecapeptide with an amino acid sequence similar to that of endogenous opioid peptide dynorphin A. Dynorphin have been reported to increase the secretion of atrial natriuretic peptide (ANP) via selective activation of kappa-opioid receptor in cultured atrial cardiocytes. The present study was designed to investigate the direct effect of N/OFQ on the ANP secretion in cultured neonatal rat cardiac myocytes via N/OFQ receptor (NOP) activation. The secretion of ANP from cultured neonatal cardiac myocytes was increased in terms of incubation time. N/OFQ, at a dose of 0.3, 1, 3, and 10 microM, caused increases in ANP secretion in a dose-dependent manner. The N/OFQ-induced ANP secretion was completely antagonized by antagonists of NOP, 1 microM each of [Phe1 (CH2-NH) Gly2] nociceptin (1-13)-NH2 ([FG]N/OFQ(1-13)NH2) or naloxone benzoylhydrazone. In contrast, naloxone (1 microM), the non-selective opioid receptor antagonist, did not alter ANP response to N/OFQ. N/OFQ at 3 microM inhibited basal and forskolin-stimulated cAMP production, which was partially antagonized with the pretreatment of [FG]N/OFQ(1-13)NH2. An increase in ANP secretion by N/OFQ was also partially blocked by the pretreatment of forskolin. Homologous competition studies in neonatal cardiomyocyte membranes revealed the presence of two distinct sites. The high affinity site (10.9 +/- 1.6 nM) was far less abundant than the low affinity site. Therefore, these results suggest that N/OFQ causes an increase in ANP secretion in cultured neonatal cardiac myocytes by decreasing cAMP through its binding sites.

Ibandronate treatment decreases the effects of tumor-associated lesions on bone density and strength in the rat

Bisphosphonate treatment is beneficial against symptoms of metastatic bone disease, although less is known about the effect of preventative treatment schedules. We investigated the effect of various treatment regimens of the bisphosphonate, ibandronate (IB), on the preservation of bone quality in a rat model of tumor-induced osteolysis. Osteolytic Walker 256 (W256) carcinosarcoma cells were implanted into the left femur of female Sprague-Dawley rats, resulting in a 10% reduction in bone mineral density (BMD), a 16% reduction in bone density (BD), and a 26% reduction in failure load compared with the right femur 28 days after implantation. IB was administered subcutaneously in five different treatment schedules: (1) IB PRE-POST received IB for 26 days, prior to implantation of W256 cells in the medullary canal of the femur, and for 28 additional days after surgery; (2) IB PRE-POST SHAM received the same IB administration, but with a sham operation; (3) IB PRE received IB injections before W256 cell insertion only; (4) IB PRE-0 received IB injections for 26 days and was then killed to serve as a time zero control; and (5) IB POST received sham injection with saline before W256 cell insertion, and then received IB injections for 28 days until killing. Controls (TUMOR ONLY) received sham injections with saline prior to W256 cell insertion, and then for 28 additional days until killing. We used dual-energy X-ray absorptiometry (DXA) to measure distal femur BMD and bone mineral content (BMC), peripheral quantitative computed tomography (pQCT) to measure distal femur BD, and torsion testing to obtain torsional failure load. Combined preventative and interventional IB treatment best preserved bone mass and strength, although all treatment schedules resulted in significant improvement compared with untreated controls (TUMOR ONLY). The possibility of reducing or even preventing skeletal morbidity in cancer patients with a high risk of developing metastatic spreading to bone is exciting, and warrants further exploration.

C-type natriuretic peptide system in rabbit colon

C-type natriuretic peptide (CNP) is mainly distributed in the brain and vascular endothelium and is considered to act as a local regulator in many tissues. The present study was aimed to determine the presence of CNP system and its biological function in rabbit colon. The serial dilution curves of tissue extracts were parallel to the standard curve of CNP-22. With gel permeation chromatography and reverse-phase HPLC, the major immunoreactive peak of CNP was observed at the same elution time corresponding to the synthetic CNP-53. The concentration of CNP in the mucosal layer of colon was 212.49 +/- 30.44 pg/g tissue wet weight (n = 7), which was significantly higher than that in the muscular layer. The presence of CNP mRNA was also detected by RT-PCR and Southern blot analysis. Production of cGMP by the activation of particulate guanylyl cyclase stimulated by BNP and CNP was higher in membranes obtained from the muscular layer than from mucosal layer. More cGMP was produced by CNP than by ANP. Both natriuretic peptide receptor-A and -B mRNAs were detected by RT-PCR and specific binding sites to 125I-[Tyr(0)]-CNP-22 were mainly localized to the muscular layer. Synthetic CNP inhibited basal tension, frequency and amplitude of basal motility of taenia coli of the right colon. This study showing the presence of CNP system and its biological function in colon suggests that endogenous CNP synthesized in the mucosal layer may have a paracrine function as a local regulator of colonic motility.

Attenuation of inhibitory effect of CNP on the secretion of ANP from hypertrophied atria

It has been shown that atrial natriuretic peptide (ANP) influences proliferation of cardiac cells. To define the possible role of C-type natriuretic peptide (CNP) in cardiac hypertrophy, the influence of CNP on the secretion of ANP was studied with the use of perfused nonbeating atria from monocrotaline-treated rats. Increases in atrial volume caused proportional increases in ANP secretion that were markedly suppressed by CNP (10(-6) M) in nonhypertrophied left atria and control right atria but not in hypertrophied right atria. However, increases in atrial volume and mechanically stimulated extracellular fluid (ECF) translocation by CNP were similar to those in the control group. Therefore, the secretion of ANP in terms of ECF translocation was decreased by CNP in nonhypertrophied left and control right atria but not in hypertrophied atria. However, the inhibitory effect of 8-bromo-cGMP on the secretion of ANP was observed in both atria. The cGMP productions from perfused hypertrophied atria and their membranes exposed to CNP were significantly lower than those from nonhypertrophied atria. No significant difference in natriuretic peptide receptor-B transcript was found. Therefore, attenuation of the inhibitory effect of CNP on the ANP secretion in hypertrophied atria may be due to lack of cGMP production. The results showing the relief of CNP-induced negative inhibition of ANP secretion by atrial hypertrophy suggest that CNP may be a contributing factor to delay the development of cardiac hypertrophy.

Accentuation of ANP secretion to endothelin-1 in hypertrophied atria

To investigate modulation of ANP secretion by atrial hypertrophy, the secretion of ANP in response to stretch and endothelin-1 was studied using isolated perfused quiescent atria from rats treated with monocrotaline (MCT). Male Sprague-Dawley rats were given a single subcutaneous injection of 50 mg/kg MCT or saline and were sacrificed at 6 weeks. Rats with right heart hypertrophy showed an increase in ANP mRNA and decrease in tissue concentration of ANP in hypertrophied atria and a marked increase in plasma concentration of ANP. In isolated perfused hypertrophied right atria from MCT rats, changes in atrial volume induced by increased atrial pressure caused proportional increases in mechanically stimulated extracellular fluid (ECF) translocation and stretch-activated ANP secretion. Changes in atrial volume and mechanically stimulated ECF translocation in hypertrophied right atria were not different from those in control right atria. The stretch-activated ANP secretion was suppressed without significant difference in basal ANP secretion, as compared to control right atria. Therefore, the stretch-activated ANP secretion from hypertrophied right atria into the atrial lumen in relation to the ECF translocation (ANP concentration in the interstitium) was lower than that from control atria. A positive correlation between the stretch-activated ANP secretion in relation to the ECF translocation and tissue ANP content was found in control atria but not in hypertrophied atria. Endothelin-1 caused increases in stretch-activated ANP secretion in a dose-dependent manner, which were accentuated in hypertrophied right atria. Therefore, we suggest that atrial hypertrophy causes an attenuated response to stretch and accentuated response to endothelin-1 of ANP secretion.

C-type natriuretic peptide system in rabbit oviduct

C-type natriuretic peptide (CNP), a third member of the natriuretic peptide family, is known to be distributed mainly in brain and vascular endothelium and is considered to act as a local regulator in many tissues. The purpose of this study was to determine the presence of CNP system and its biological function in rabbit oviduct. The serial dilution curve of tissue extracts was parallel to the standard curve of CNP((1-22)) and a major peak of molecular profile of tissue extracts by HPLC was CNP((1-53)). mRNA of CNP which was the same size as positive control was also detected by Southern blot analysis. CNP increased the production of 3',5'-cyclic guanosine monophosphate (cGMP) in the purified membrane of oviduct, which was more in membranes derived from the isthmic portion than in the ampullar portion. The presence of mRNAs of natriuretic peptide receptor-A (NPR-A) and NPR-B was demonstrated by RT-PCR. Synthetic CNP((1-22)) inhibited both frequency and amplitude of basal motility of oviduct in a dose-dependent manner. The inhibitory effect of CNP on the basal motility was more potent in the isthmic portion than in the ampullar portion. These results demonstrate the presence of CNP system in the oviduct and regional differences in motility inhibition by CNP between isthmic and ampullar portions. Therefore, these findings suggest the possible existence of a CNP system that may exert a local regulator of basal motility, either alone or in concert with other hormones.

Distinct roles for L- and T-type Ca(2+) channels in regulation of atrial ANP release

Atrial secretion of atrial natriuretic peptide (ANP) has been shown to be regulated by atrial workload. Although modulating factors for the secretion of ANP have been reported, the role for intracellular Ca(2+) on the secretion of ANP has been controversial. The purpose of the present study was to define roles for L- and T-type Ca(2+) channels in the regulation of ANP secretion in perfused beating rabbit atria. BAY K 8644 (BAY K) increased atrial stroke volume and pulse pressure. BAY K suppressed ANP secretion and ANP concentration in terms of extracellular fluid (ECF) translocation concomitantly with an increase in atrial dynamics. BAY K shifted the relationship between ANP secretion and ECF translocation downward and rightward. These results indicate that BAY K inhibits myocytic release of ANP. In the continuous presence of BAY K, diltiazem reversed the effects of BAY K. Diltiazem alone increased ANP secretion and ANP concentration along with a decrease in atrial dynamics. Diltiazem shifted relationships between ANP secretion and atrial stroke volume or ECF translocation leftward. The T-type Ca(2+) channel inhibitor mibefradil decreased atrial dynamics. Mibefradil inhibited ANP secretion and ANP concentration in contrast with the L-type Ca(2+) channel inhibitor. These results suggest that activation of L- and T-type Ca(2+) channels elicits opposite effects on atrial myocytic release of ANP.

Hepatocellular carcinoma despite long-term survival in chronic tyrosinaemia I

Tyrosinaemia I (fumarylacetoacetate hydrolase deficiency) is an autosomal recessive inborn error of tyrosine metabolism that produces liver failure in infancy or a more chronic course of liver disease with cirrhosis, often complicated by hepatocellular carcinoma, in childhood or early adolescence. We studied a 37-year-old woman with tyrosinaemia I whose severe liver disease in infancy and rickets during childhood resolved with dietary therapy. From 14 years of age she resumed an unrestricted diet with the continued presence of the biochemical features of tyrosinaemia, yet maintained normal liver function. In adult years she accumulated only small amounts of succinylacetone. Despite this evolution to a mild biochemical and clinical phenotype, she eventually developed hepatocellular carcinoma. Her fumarylacetoacetate hydrolase genotype consists of a splice mutation, IVS6-1g>t, and a novel missense mutation, Q279R. Studies of resected liver demonstrated the absence of hydrolytic activity and of immunological expression of fumarylacetoacetate hydrolase in liver tumour. In nontumoral areas, however, 53% of normal hydrolytic activity and immunologically present fumarylacetoacetate hydrolase was found. This case demonstrates the high risk of liver cancer in tyrosinaemia I even in a seemingly favourable biological environment.

Cyclosporine impairs the guanylyl cyclase activity of the natriuretic peptide receptor in the glomerulus

In order to elucidate the involvement of the atrial natriuretic peptide (ANP) and its receptor (natriuretic peptide receptor; NPR) system in cyclosporine-induced nephrotoxicity, we investigated the cyclosporine A (CsA)-induced changes in characteristics of the NPR/guanylyl cyclase system in the glomerulus and inner medulla of the rat kidney. CsA was administered intramuscularly to rats for 2 weeks (CsA group). Particulate guanylyl cyclase activity was measured in glomerular and inner medullary membranes. For receptor characteristics, quantitative in vitro receptor autoradiography was performed. The guanylyl cyclase activity in the glomerulus from the CsA group was attenuated compared with that from the control. However, the activity in the inner medulla was not affected by CsA treatment. Direct application of CsA to normal glomerular membrane completely abolished the ANP-induced guanylyl cyclase activation. Binding studies, using(125)I-ANP, revealed that B(max)was decreased in the CsA group, while K(d)was not affected in the glomerulus. However, in the inner medulla, neither B(max)nor K(d)was affected by CsA treatment. CsA did not displace the(125)I-ANP bindings to NPRs in the normal rat kidney. Local tissue ANP as well as plasma ANP concentration in both groups was not significantly different. These results indicate that CsA impairs the guanylyl cyclase activity mainly in the glomerulus by the decrease in NPR population and/or by direct inhibition, suggesting that the ANP/NPR system might be involved in CsA-induced nephrotoxicity.

Natriuretic peptide system in the rat lacrimal gland

The presence and characteristics of the natriuretic peptides and their receptors in the rat exorbital lacrimal gland were investigated. Serial dilution curves of the gland extracts were parallel to the standard curves of synthetic atrial natriuretic peptide (ANP) or C-type natriuretic peptide (CNP). Immunoreactive ANP or CNP in the gland extracts co-eluted with authentic ANP or CNP, and their contents were 4.95 +/- 0.60 and 2.87 +/- 0.53 pg mg(-1)protein (quadruplicate), respectively. By immunohistochemistry, strong immunoreactivities of ANP and CNP were co-localized in the tubules and excretory ducts of the gland, and moderate immunoreactivities were found in the myoepithelial cells and acini. Productions of guanosine 3',5'-cyclic monophosphate by particulate guanylyl cyclase in the gland membranes were stimulated by natriuretic peptides in a dose-dependent manner, and that by CNP was larger than by ANP. Messenger RNAs for ANP, CNP and their receptors were detected by reverse transcription-polymerase chain reaction. These results indicate that natriuretic peptides and their specific receptors are found in the rat lacrimal gland. Therefore, it is suggested that natriuretic peptide system may play physiological roles in the rat lacrimal gland.

Effects of pituitary adenylate cyclase activating polypeptide27 on cyclic AMP efflux and atrial dynamics in perfused beating atria

Although pituitary adenylate cyclase activating polypeptide (PACAP) has been shown to increase cardiac force of contraction and to change the heart rate, the effect of PACAP on cyclic (c) AMP production in the atrium still has to be defined. In the present experiments, a simple protocol was developed for the evaluation of cAMP production in real-time base in the perfused beating left atria. The PACAP27-induced cAMP efflux in the atrial perfusate reflected changes in the production of cAMP in the atrial tissue. cAMP efflux was measured as an indicator of cAMP production in beating perfused rabbit atria. PACAP27 increased cAMP production in a dose- and time-dependent manner with a minor effect on atrial dynamics. These results suggest that PACAP27 has other roles besides control of force of contraction through cAMP production in the atrium.

Coexistence of C-type natriuretic peptide and atrial natriuretic peptide systems in the bovine cornea

PURPOSE

To determine whether the cornea synthesizes natriuretic peptides and contains their receptors.

METHODS

The synthesis of the natriuretic peptides, C-type natriuretic peptide (CNP) and atrial natriuretic peptide (ANP), in the bovine cornea was determined by high-performance liquid chromatography (HPLC) with radioimmunoassay and Southern blot analysis. The presence of natriuretic peptide receptor (NPR)-A and -B and their localizations were measured by reverse transcription-polymerase chain reaction (RT-PCR), in vitro autoradiography, and the activation of particulate guanylyl cyclase by natriuretic peptides in the corneal membrane.

RESULTS

The serial dilution curves of corneal extracts were parallel to the standard curves of CNP and ANP. With reversed-phase HPLC, a major immunoreactive peak of CNP or ANP was observed at the elution time corresponding with synthetic CNP(1-53) or atriopeptin III (APIII), respectively. The presence of mRNAs of CNP and ANP was also detected in the cornea by RT-PCR and/or Southern blot analysis. Production of 3',5'-cyclic guanosine monophosphate (cGMP) by the activation of particulate guanylyl cyclase in the corneal membrane was stimulated by ANP, BNP, and CNP. More cGMP was produced by CNP than by the other natriuretic peptides. Specific 125I-[Tyr0]-CNP(1-22) binding sites were localized in the endothelial cell layer of cornea. The apparent dissociation constant (Kd) value of the cornea was 3.06 +/- 0.73 nM and the maximum binding capacity was 3.40 +/- 0.63 femtomoles/mm2. Both NPR-A and NPR-B mRNAs were detected by RT-PCR.

CONCLUSIONS

The cornea synthesizes CNP and ANP and contains their receptors. These results suggest that the CNP and ANP systems coexist in the bovine cornea.

Renin angiotensin system of rabbit clitoral cavernosum: interaction with nitric oxide

PURPOSE

Angiotensin (ANG) II has been known to be a potent modulator for the maintenance of smooth muscle tone of the penile cavernosum. However, its role in clitoral cavernosum is unknown. The clitoris is the homologue of the penis arising from the embryological genital tubercle. We investigated the presence of ANG II receptors, the function of ANG II, and its interaction with nitric oxide (NO) in rabbit clitoral cavernosum.

MATERIALS AND METHODS

The isometric tension was measured in the strips of clitoral cavernosum. Reverse transcriptase polymerase chain reaction (RT-PCR) was used to evaluate expression of AT1a and AT1b ANG II receptor subtype mRNAs. In vitro autoradiography was used to localize ANG II receptors in the clitoral cavernosum.

RESULTS

The clitoral cavernosum was contracted dose-dependently by the addition of ANG II. Dup 753 (ANG II type 1 receptor antagonist) inhibited significantly ANG II induced contraction. PD 123,319 (ANG II type 2 receptor antagonist) did not affect the ANG II response. Pretreatment with NG-nitro-L-arginine methyl ester (NO synthase inhibitor) accentuated contractions induced by ANG II. Specific binding sites for 125I-ANG II were found in the clitoral cavernosum. The dissociation constant (Kd) was 0.58 + or - 0.05 nM. Specific binding of 125I-ANG II was displaced by Dup 753 (10-5 M) but not by PD 123,319 (10-5 M). The inhibitory constant (Ki) for Dup 753 was 23. 4 + or - 9.73 nM and mRNAs for AT1a and AT1b receptor subtypes were detected by RT-PCR.

CONCLUSION

The present study shows that ANG II is involved in the regulation of clitoral cavernosum smooth muscle tone via ANG II receptor subtype AT1, and that ANG II has cross-talk with NO.

Immunohistochemical localization of C-type natriuretic peptide in the rat submaxillary salivary gland

To define the localization and characteristics of C-type natriuretic peptide (CNP) in the rat submaxillary gland, immunohistochemistry and gel permeation-high-performance liquid chromatography were used. Immunoreactive (IR)-CNP was localized in cells of the granular convoluted tubule, striated duct and endothelial cells of the capillary, where atrial natriuretic peptide (ANP) was colocalized in consecutive sections, but not in acini. Gland extracts co-eluted with synthetic CNP and its content was 60.3+/-4.9 pg/mg protein (n=4). Molecular profiles of immunoreactive material showed two peaks corresponding to synthetic CNP((1-53)) and CNP((1-22)). These results indicate that CNP is colocalized with ANP in the duct and endothelial cells of the rat submaxillary gland. Therefore, CNP may have a physiological role in the submaxillary gland by interacting with ANP and/or other biologically active substances in the ducts and granular convoluted tubule cells.

Ectopic expression of active processed form of atrial natriuretic peptide in skeletal myoblasts

Atrial natriuretic peptide (ANP) is a cardiac hormone that elicits a profound diuresis, natriuresis, and hypotension. As a preliminary study toward ANP gene therapy of cardiovascular disorders, we have cloned a cDNA for mouse preproANP and carried out expression studies in muscle cells. The expression cassette, which was flanked by ITRs from AAV-2, consisted of HCMV IE enhancer/promoter, preproANP gene, and polyadenylation signal from bovine growth hormone. We transfected this expression vector into primary skeletal myoblasts and examined the following points: (1) secretion of immunoreactive ANP, (2) biological activity, and (3) nature of secreted ANP(s). The conditioned media from cells transfected with ANP vector had significantly higher levels of irANP in comparison to mock control. The secreted irANP had biological activity as confirmed by the elevated level of intracellular cGMP in human umbilical vein endothelial cells. Reverse-phase HPLC analysis showed that the processed form of ANP was the predominant form. These results demonstrate that preproANP gene could be ectopically expressed and correctly processed in skeletal myoblasts, which has implications for development of muscle-based ANP gene therapy.

Localization of receptors for natriuretic peptide and endothelin in the duct of the epididymis of the freshwater turtle

The presence of receptor subtypes for natriuretic peptides (NPs) and endothelin (ET) in the epididymis of the freshwater turtle, Amyda japonica, was examined by quantitative in vitro autoradiography using iodinated mammalian-type atrial NP ((125)I-ANP((1-28))), phylogenically conserved C-type NP ((125)I-[Tyr(0)]-CNP((1-22))), and ET-1 ((125)I-ET-1) as radiolabeled ligands. To characterize NP receptor (NPR) subtypes, we also performed an activation of particulate guanylyl cyclase (GC) in membranes of the epididymis by NPs. Specific (125)I-ANP((1-28)) and (125)I-[Tyr(0)]-CNP((1-22)) bindings were localized in surrounding smooth muscle cell layer of the duct of the epididymis with an apparent dissociation constant (K(d)) of 0.84+/-0.15 and 1.74+/-0.39 nM and a maximal binding capacity (B(max)) of 0.47+/-0.11 and 0.08+/-0.01 fmol/mm(2), respectively. Bindings of (125)I-ANP((1-28)) and (125)I-[Tyr(0)]-CNP((1-22)) to these sites were also displaced by des[Gln(18),Ser(19),Gly(20), Leu(21),Gly(22)]ANF((4-23)), a specific ligand of the NP clearance receptor. Production of 3',5'-cyclic guanosine monophosphate by particulate GC in membranes of the epididymis was stimulated by ANP((1-28)), BNP((1-26)), and CNP((1-22)). Receptor subtypes for ET in the epididymis were characterized by competition with BQ 123 and BQ 788 as specific antagonists for ET receptors, type A (ET(A)) and type B (ET(B)) subtypes, respectively. Specific (125)I-ET-1 bindings were localized in the smooth muscle cell layer of the duct of the epididymis with K(d) and B(max) of 0.21+/-0.03 nM and 0.52+/-0.05 fmol/mm(2), respectively. These specific bindings were potently inhibited in a dose-dependent manner by BQ 123, whereas BQ 788 (10 microM) was not in competing for specific (125)I-ET-1 bindings in this structure. Therefore, these results indicate that specific NP and ET receptors are localized in surrounding smooth muscle cells of the duct of the epididymis of the freshwater turtle. It is also suggested that biological and clearance NPR-like subtypes coexist in these cells, and the predominant ET receptor subtype in this tissue is the ET(A)-like receptor. The localization of specific receptors for NPs and ET in the epididymis may be involved in the control of the transport of sperm in the freshwater turtle.

Diminished adenylate cyclase activity and aquaporin 2 expression in acute renal failure rats

BACKGROUND

The present study was aimed at investigating the changes of aquaporin 2 (AQP2) expression and its underlying mechanisms in ischemic acute renal failure (ARF).

METHODS

ARF was induced by clamping the both renal arteries for 60 minutes in rats. Two or seven days later, AQP2 expression and trafficking were determined in the kidney by Western blot analysis and immunohistochemistry. The activity of adenylate cyclase was also measured.

RESULTS

The urinary flow rates in ARF-2 and ARF-7 day were significantly increased in association with decreases of urine osmolality. While there was decreased expression of AQP2 in the cortex, outer medulla, and inner medulla in ARF, it was most pronounced in the outer medulla. The AQP2 expression was reduced in the apical membrane-enriched fraction as well the subapical vesicle-enriched fraction in ARF; however, the degree was greater in the former than in the latter. Immunohistochemical study also showed a markedly decreased expression of AQP2 in the collecting duct in ARF. cAMP generation in response to arginine vasopressin (AVP) in the kidney was attenuated in ARF, most prominently in the outer medulla. cAMP generation in the outer medulla in response to forskolin was not affected, but sodium fluoride was significantly blunted in ARF.

CONCLUSIONS

The AVP-stimulated adenylate cyclase activity is impaired in ARF, secondary to a defect at the level of the G protein. The expression of AQP2 was reduced as a consequence, which may in part account for urinary concentration defect in ARF.

[Anti-osteolytic therapy preserves trabecular structure and mechanical properties of bone in tumor osteolysis]

PURPOSE OF THE STUDY

Little is known about the effect of a tumor on the trabecular architecture, therefore we employed an animal model for the assessment of bone quality in tumor osteolysis to determine the alterations of the trabecular architecture in tumor osteolysis and after an interventional treatment with a bisphosphonate.

METHODS

To assess the bone mass and the micro-architecture of the trabecular bone in tumor osteolysis we employed a micro-computed tomography system. For the assessment of the mechanical properties of the treated and non-treated tumor-bearing bones we used a torsion test.

RESULTS

The presence of a tumor in bone resulted in a reduction of bone mass, stability and architectural parameters. An interventional treatment of the animals with a bisphosphonate increased the bone mineral content, mechanical and architectural parameters compared to the non-treated, tumor-bearing animals.

CONCLUSIONS

These results clearly show a beneficial effect of an anti-osteolytic treatment with a bisphosphonate in regard of bone quality in tumor-induced osteolysis.

C-type natriuretic peptide inhibits ANP secretion and atrial dynamics in perfused atria: NPR-B-cGMP signaling

The purpose of the present experiments was to define the role of C-type natriuretic peptide (CNP) in the regulation of atrial secretion of atrial natriuretic peptide (ANP) and atrial stroke volume. Experiments were performed in perfused beating and nonbeating quiescent atria, single atrial myocytes, and atrial membranes. CNP suppressed in a dose-related fashion the increase in atrial stroke volume and ANP secretion induced by atrial pacing. CNP caused a right shift in the positive relationships between changes in the secretion of ANP and atrial stroke volume or translocation of the extracellular fluid (ECF), which indicates the suppression of atrial myocytic release of ANP into the paracellular space. The effects of CNP on the secretion and contraction were mimicked by 8-bromoguanosine 3',5'-cyclic monophosphate (8-BrcGMP). CNP increased cGMP production in the perfused atria, and the effects of CNP on the secretion of ANP and atrial dynamics were accentuated by pretreatment with an inhibitor of cGMP phosphodiesterase, zaprinast. An inhibitor of the biological natriuretic peptide receptor (NPR), HS-142-1, attenuated the effects of CNP. The suppression of ANP secretion by CNP and 8-BrcGMP was abolished by a depletion of extracellular Ca(2+) in nonbeating atria. Natriuretic peptides increased cGMP production in atrial membranes with a rank order of potency of CNP > BNP > ANP, and the effect was inhibited by HS-142-1. CNP and 8-BrcGMP increased intracellular Ca(2+) concentration transients in single atrial myocytes, and mRNAs for CNP and NPR-B were expressed in the rabbit atrium. From these results we conclude that atrial ANP release and stroke volume are controlled by CNP via NPR-B-cGMP mediated signaling, which may in turn act via regulation of intracellular Ca(2+).

Treatment with ibandronate preserves bone in experimental tumour-induced bone loss

Cancer-induced bone diseases are often associated with increased bone resorption and pathological fractures. In recent years, osteoprotective agents such as bisphosphonates have been studied extensively and have been shown to inhibit cancer-related bone resorption in experimental and clinical studies. The third-generation bisphosphonate, ibandronate (BM 21.0955), is a potent compound for controlling tumour osteolysis and hypercalcaemia in rats bearing Walker 256 carcinosarcoma. We have studied the effect of ibandronate given as an interventional treatment on bone strength and bone loss after the onset of tumour growth in bone. Our results suggest that it is capable of preserving bone quality in rats bearing Walker 256 carcinosarcoma cells. Since other bisphosphonates have produced comparable results in man after their success in the Walker 256 animal models our findings suggest that ibandronate may be a powerful treatment for maintaining skeletal integrity in patients with metastatic bone disease.

Modulation of endocardial natriuretic peptide receptors in right ventricular hypertrophy

Natriuretic peptide (NP) receptors (NPRs) located at the endocardial endothelium are suggested to be involved in regulating myocardial contractility. However, the characteristics and modulation of NPRs in relation to cardiac failure are not well defined. This study examined the properties of NPRs in ventricular endocardium using quantitative receptor autoradiography, RT-PCR, Southern blot analysis, and activation of particulate guanylyl cyclase (GC) by NPs. In control rats, specific 125I-labeled rat atrial NP (rANP)(1-28) binding sites were localized in right (RV) and left ventricular (LV) endocardium. Binding affinities of 125I-rANP(1-28) were remarkably higher in RV than LV endocardium. Radioligand binding at these sites was mostly inhibited by des[Gln18,Ser19,Gly20,Leu21, Gly22]ANP(4-23), a specific NP clearance receptor ligand. mRNAs for all three recognized NPRs were detected in endocardial cells by RT-PCR and confirmed by Southern blot analysis. Production of cGMP by particulate GC in endocardial cell membranes was stimulated by NPs with a rank order of potency of C-type NP(1-22) >> brain NP (BNP)(1-26) > ANP(1-28). We also examined the modulation of these NPRs during cardiac hypertrophy induced by monocrotaline (MCT). In MCT-treated rats with pulmonary hypertension, specific (125)I-rANP(1-28) binding to hypertrophied RV endocardium almost disappeared and cGMP production by NPs was significantly decreased. In rats with pulmonary hypertension, plasma levels of ANP and BNP were increased by fivefold compared with controls. The results indicate that there is a differential distribution of NPRs in the cardiac chambers, with the most abundant binding sites in RV endocardium, that NPR-B is the predominant GC-coupled NPR in ventricular endocardium, and that endocardial NPRs are downregulated with ventricular hypertrophy. Downregulation of NPRs may be associated with an increment of endogenous NP production caused by mechanical overload in hypertrophied ventricle.

Localization of atrial natriuretic peptide receptors in the rat tongue and hard palate

Atrial natriuretic peptide (ANP) receptors were characterized in rat oral mucosa using quantitative in vitro autoradiography and activation of particulate guanylyl cyclase (GC) by natriuretic peptides. Competition-binding analysis performed by quantitative in vitro autoradiography demonstrated specific [125I]rANP(1-28) binding sites in the tongue and hard palate. The precise location of this binding was revealed on the basal and parabasal cells of the epithelia by microautoradiography. The dissociation constant (Kd) and maximal binding capacity (Bmax) of these sites were 3.34+/-1.35 nM and 2.71+/-2.21 fmol/mm2 on the epithelium of the tongue, and 4.09+/-1.52 nM and 3.45+/-3.01 fmol/mm2 on the epithelium of the hard palate, respectively. Receptor subtypes were characterized by competition with des [Gln18, Ser19, Gly20, Leu21, Gly22] ANP(4-23) (C-ANP), a specific ligand for the clearance receptor (NPR-C). These binding sites were displaced by C-ANP with inhibition constant (Ki) of 8.96+/-3.18 nM and Bmax of 2.89+/-2.45 fmol/mm2 on the epithelium of the tongue, and Ki of 9.12+/-2.71 nM and Bmax of 3.08+/-2.94 fmol/mm2 on the epithelium of the hard palate, respectively. Production of cyclic GMP by particulate GC in the epithelial membranes of the tongue and hard palate was stimulated by rANP(1-28), porcine brain natriuretic peptide (BNP)(1-26), and C-type natriuretic peptide (CNP)(1-22) in a dose-dependent manner. These results indicate that ANP-binding sites in the epithelium of the tongue and hard palate are mainly clearance receptors (NPR-C) but biological receptors (NPR-A and/or NPR-B) with GC activity are also present, and suggest that ANP may have a role in the proliferation of the oral epithelial cells, especially in the tongue and hard palate.

Presence and biological activity of C-type natriuretic peptide-dependent guanylate cyclase-coupled receptor in the penile corpus cavernosum

PURPOSE

To investigate the presence of C-type natriuretic peptide 1-22 (CNP)-dependent guanylyl cyclase (GC)-coupled receptor and its biological function in the penile erectile smooth muscle.

MATERIALS AND METHODS

Experiments have been done in rabbit and rat to detect cyclic GMP (cGMP) generation by the activation of particulate GC by natriuretic peptides (NPs) in cavernosal membrane, to localize precise receptor using a quantitative in vitro autoradiography of the snap frozen sections, to define natriuretic peptide receptor (NPR) mRNA using a reverse transcriptase-polymerase chain reaction (RT-PCR) technique and to monitor changes of erectile smooth muscle tone by NPs in the penile tissue strips.

RESULTS

Productions of cGMP by particulate GC in the corpus cavernosum membranes of rabbit and rat were stimulated by CNP, atrial natriuretic peptide 1-28 (ANP) and brain natriuretic peptide 1-26 (BNP) with a rank order of potency of CNP > BNP > ANP. HS-142-1, a selective antagonist for the GC-coupled NPR, inhibited the CNP-stimulated cGMP production in corpus cavernosal membrane of rabbit and rat. Specific 125I-(Tyr[0])-CNP bindings were localized in the corpus cavernosal smooth muscle of rabbit with Kd of 19.92+/-3.38 nM. and Bmax of 734.64+/-139.63 amol./mm2. B-subtype of NPR mRNA was detected in the penile corpus cavernosum of rat using RT-PCR technique. CNP relaxed the smooth muscle contracted by Nomega-nitro-L-arginine methylester (L-NAME).

CONCLUSIONS

These results suggest for the first time that CNP modulates the erectile smooth muscle tone of penis by predominant activation of B-subtype of NPR with augmentation of cGMP production via particulate GC.

Overlapping distribution of receptors for atrial natriuretic peptide and angiotensin II in the kidney and the adrenal gland of the freshwater turtle, Amyda japonica

The distribution of receptors for atrial natriuretic peptide (ANP) and angiotensin II (ANG II) in the kidney and adrenal gland of the freshwater turtle, Amyda japonica, was examined by quantitative in vitro autoradiography using 125I-labeled rat (r)ANP1-28 and 125I-labeled human ANG II as labeled ligands. Receptor subtypes were characterized by competition with des[Gln18,Ser19,Gly20, Leu21, Gly22] ANP(4-23) (C-ANP) as a selective ligand of the clearance receptors to specific 125I-rANP(1-28) binding, and with DuP 753 and PD 123319 as nonpeptide antagonists for ANG II receptors type 1 (AT1) and type 2 (AT2) subtypes, respectively, to 125I-ANG II binding. Specific 125I-rANP(1-28) binding with a single binding site was found overlying glomeruli of the kidney and the outer zone of the adrenal gland with dissociation constants (Kd) of 4.39 +/- 0.33 and 6.07 +/- 1.36 nM, respectively. C-ANP (10 microM) inhibited about 90% of the glomerular and adrenal 125I-rANP(1-28) binding. Specific 125I-ANG II binding was also localized in the glomeruli of the kidney and the outer zone of the adrenal gland with Kd of 1.02 +/- 0.22 and 0.37 +/- 0.04 nM, respectively. DuP 753 (10 microM) potently inhibited about 80% of glomerular and 90% of adrenal 125I-ANG II binding, whereas PD 123319 (10 microM) was very weak in competing for specific 125I-ANG II binding in both tissues. Therefore, these results indicate that specific ANP and ANG II receptors with high affinities have an overlapping distribution in glomeruli of the kidney and the outer zone of the adrenal gland of the freshwater turtle. They also suggest that biological and clearance ANP receptor-like subtypes coexist in both tissues, and the predominant ANG II receptor subtype in these tissues is the AT1-like receptor. The overlapping distribution of specific receptors for both peptides in these tissues provides the basis for possible receptor interactions to exert a functional antagonism between ANP and ANG II in the freshwater turtle.

Renin angiotensin system in rabbit corpus cavernosum: functional characterization of angiotensin II receptors

PURPOSE

The regulation of the corporal smooth muscle tone is important in the process of penile erection. Although specific angiotensin (ANG) II binding to and effects of ANG II on some reproductive structures have been studied, the presence of the renin-angiotensin system has not yet been defined in the corpus cavernosum. ANG II is formed from ANG I by angiotensin I-converting enzyme (ACE). ANG II and ANG I produce contractions in vascular smooth muscles. Two subtypes of ANG II receptors (AT1 and AT2) have been characterized. The purpose of the present experiments was to determine whether the renin-angiotensin system regulates rabbit corpus cavernosum smooth muscle tone.

MATERIALS AND METHODS

A strip of rabbit corpus cavernosum was mounted in an organ chamber to measure the isometric tension. The specific binding for 125I-ANG II was characterized by in vitro autoradiography.

RESULTS

ANG II and ANG I, precursor of ANG II, contracted corpus cavernosum smooth muscle dose-dependently, but the response of smooth muscle to ANG I was 10-fold less than that to ANG II. Contractile responses of smooth muscle to ANG II and ANG I were blocked by Dup 753, a specific inhibitor of ANG II type 1 receptor, but not by PD 123,319, a specific inhibitor of ANG II type 2 receptor. The effect of ANG I was attenuated by captopril, an inhibitor of ACE. Specific binding sites for 125I-ANG II were found in the corpus cavernosum. The dissociation constant (Kd) was 5.32 +/- 1.65 nM. and maximum binding capacity (Bmax) was 305.72 +/- 85.24 amol/mm. Specific binding of 125I-ANG II was displaced by Dup 753 (10(-6) M) but not by PD 123,319 (10(-5) M). The inhibitory constant (Ki) for Dup 753 was 8.09 +/- 2.51 nM.

CONCLUSION

The present results suggest that the renin-angiotensin system is involved in the regulation of corpus cavernosum smooth muscle tone of rabbit and the ANG II receptor subtype AT1 is important in the regulation of penile erection.

Glibenclamide suppresses stretch-activated ANP secretion: involvements of K+ATP channels and L-type Ca2+ channel modulation

The mechanism by which glibenclamide regulates mechanically activated atrial natriuretic peptide (ANP) secretion was investigated using isolated perfused rat atria. A reduction in atrial pressure from an experimentally imposed distending pressure stimulated the secretion of ANP and caused concomitant translocation of extracellular fluid (ECF) into the atrial lumen. The activation of ANP secretion and ECF translocation were closely correlated with atrial volume changes and the increase in ANP secretion was a function of the ECF translocation. Glibenclamide (1, 10, 100 microM), an ATP-sensitive K+ (K+ATP) channel blocker, had no effect on the basal secretion of ANP, suppressed the stimulation of stretch-activated ANP secretion in a dose-dependent manner, but not the translocation of the ECF. Glipizide (100 microM) and tolbutamide (100 microM), other K+ATP channel blockers, had similar effects to those of glibenclamide. Suppression by glibenclamide (100 microM) of the stretch-induced ANP secretion was not observed in atria that had been pretreated with pinacidil (200 microM), an ATP-sensitive K+ channel opener: pinacidil alone had no effect on ECF translocation and ANP secretion. Furthermore, blocking Ca2+ influx by using the Ca2+ channel blocker diltiazem (10 nM), or a Ca2+-depleted medium prevented the suppression of stretch-induced ANP secretion by glibenclamide. In other experiments, atrial distension produced a slight membrane depolarization of cardiomyocytes; this was accentuated in the presence of glibenclamide. Furthermore, in single cardiomyocytes, glibenclamide increased the intracellular Ca2+ concentration ([Ca2+]i) in a dose-dependent manner. From these results, we suggest that glibenclamide suppresses atrial release of ANP by blocking K+ATP channels and increasing Ca2+ influx and that the K+ATP channels are associated with the regulation of the mechanically activated ANP secretion from the atria.

Renin angiotensin system in rabbit corpus cavernosum: functional characterization of angiotensin II receptors

PURPOSE

The regulation of the corporal smooth muscle tone is important in the process of penile erection. Although specific angiotensin (ANG) II binding to and effects of ANG II on some reproductive structures have been studied, the presence of the renin-angiotensin system has not yet been defined in the corpus cavernosum. ANG II is formed from ANG I by angiotensin I-converting enzyme (ACE). ANG II and ANG I produce contractions in vascular smooth muscles. Two subtypes of ANG II receptors (AT1 and AT2) have been characterized. The purpose of the present experiments was to determine whether the renin-angiotensin system regulates rabbit corpus cavernosum smooth muscle tone.

MATERIALS AND METHODS

A strip of rabbit corpus cavernosum was mounted in an organ chamber to measure the isometric tension. The specific binding for 125I-ANG II was characterized by in vitro autoradiography.

RESULTS

ANG II and ANG I, precursor of ANG II, contracted corpus cavernosum smooth muscle dose-dependently, but the response of smooth muscle to ANG I was 10-fold less than that to ANG II. Contractile responses of smooth muscle to ANG II and ANG I were blocked by Dup 753, a specific inhibitor of ANG II type 1 receptor, but not by PD 123,319, a specific inhibitor of ANG II type 2 receptor. The effect of ANG I was attenuated by captopril, an inhibitor of ACE. Specific binding sites for 125I-ANG II were found in the corpus cavernosum. The dissociation constant (Kd) was 5.32 +/- 1.65 nM. and maximum binding capacity (Bmax) was 305.72 +/- 85.24 amol/mm. Specific binding of 125I-ANG II was displaced by Dup 753 (10(-6) M) but not by PD 123,319 (10(-5) M). The inhibitory constant (Ki) for Dup 753 was 8.09 +/- 2.51 nM.

CONCLUSION

The present results suggest that the renin-angiotensin system is involved in the regulation of corpus cavernosum smooth muscle tone of rabbit and the ANG II receptor subtype AT1 is important in the regulation of penile erection.

Characterization of the atrial natriuretic peptide system in the oviduct

The atrial natriuretic peptide (ANP) gene is expressed in several extraatrial tissues in which ANP may be involved in the regulation of autocrine or paracrine functions. In the ovary, the synthesis of ANP, its binding sites, and a physiological role were found. The ANP system in the oviduct, however, is yet to be defined. The purpose of the present study was to determine whether the ANP system is present in the oviduct and then to define its function. The serial dilution curves of oviductal extracts in rat and rabbit were parallel to the standard curve of ANP. Molecular profiles using reverse phase HPLC indicated that the prohormone and processed circulating peptide were the main forms present. The immunoreactive ANP content of the oviduct was 27.07 +/- 4.41 pg/mg tissue wet wt (1.19 +/- 0.19 ng/oviduct; n = 10; at metestrus) in rats and 1.21 +/- 0.12 pg/mg tissue wet wt (0.15 +/- 0.01 ng/oviduct; n 12) in rabbits. In adult 4-day cycling rats, the immunoreactive ANP contents in oviducts had a cyclic change characterized by the lowest level at proestrus (14.59 +/- 3.24 pg/mg; n = 12). A distinct and strong ANP immunoreactivity was found in the mucosal layer of rat oviduct, and ANP messenger RNA was also detected in the oviduct by reverse transcriptase-PCR. Specific high affinity binding sites for iodinated rat ANP ([125I]rANP) were observed in the mucosal layer of the oviduct in rats and rabbits. Specific [125I]rANP bindings localized in the mucosal layer of rabbit oviduct showed an apparent dissociation constant (Kd) of 18.69 +/- 5.55 nM and a maximal binding capacity of 14.85 +/- 6.19 fmol/mm2. These specific [125I]rANP bindings were not reversed by des-[Gln18,Ser19,Gly20,Leu21,Gly22]ANP-(4- 23) as a selective ligand of clearance receptor. Synthetic ANP inhibited both the frequency and amplitude of basal motility of rabbit oviduct in a dose-dependent manner. These results suggest that the oviduct has its own ANP system, and the system is involved in the regulation of oviductal motility.

Hydroxyprolinemia: comparison of a patient and her unaffected twin sister

Hydroxyproline is a major constituent of collagen. It accumulates as the free imino acid in a rarely reported inborn error of metabolism known as hydroxyprolinemia. This metabolic disorder was initially described in association with mental retardation, but subsequent identification in clinically normal individuals has led to the supposition that it is benign. The possibility that hydroxyprolinemia might have an adverse effect on cognitive development without producing mental retardation has not been determined nor has its incidence been reported. We prospectively studied a girl with untreated hydroxyprolinemia identified by routine neonatal urine screening, the only infant found among 1 million screened, and compared her with her unaffected dizygotic twin sister. Plasma and urine hydroxyproline were increased approximately 10-fold and 100-fold, respectively, in the affected twin. Both girls have had normal growth, with the affected twin taller than her sister. On neuropsychologic testing, the affected twin was within normal limits, performing slightly better than her sister on verbal and achievement tests but less well on visual perceptual testing. It appears that hydroxyprolinemia has caused no physical or general cognitive deficits. The possibility of an effect on visual perceptual functioning, although unlikely, cannot be eliminated.

Specific binding sites for atrial natriuretic peptide in the freshwater turtle, Amyda japonica

Specific binding sites for atrial natriuretic peptide (ANP) were investigated by in vitro autoradiographic techniques in various tissues of the freshwater turtle, Amyda japonica. A high density of binding sites for 200 pM of 125I-labelled rANP(1-28) was located in the glomeruli of the kidney and the cortical portion of the adrenal gland. A moderate density of binding sites was seen in the arachnoid matter and choroid plexus of the third and lateral ventricles of the brain and the epididymis. A low density of binding sites was revealed in lamina propria of the mucosa of stomach and intestine, the seminiferous tubules of testes, and the epithelial layer of oviduct. In the presence of excess unlabelled rANP(1-28) (1 microM), binding to these structures were completely displaced. Therefore, specific ANP receptors exist in the kidney, adrenal gland, stomach, intestine, oviduct, epididymis, seminiferous tubules and brain. The ANP system may be involved in physiological regulatory function in the freshwater turtle, Amyda japonica.

Atrial natriuretic peptide immunoreactivity in the eggs of the silkworm Bombyx mori

Synthesis and secretion of atrial natriuretic peptides (ANPs) are not confined to the atrium, but are also present in other tissues. Recently, we have found synthesis of ANP in the eggs of several vertebrate animals. The present study was undertaken to determine whether immunoreactive ANP (irANP) is present in the egg of an invertebrate, the silkworm (Bombyx mori L.). The serial dilution curve of egg extracts of silkworm was parallel to the standard curve of atriopeptin III. Analysis of ANP immunoreactivity by gel filtration chromatography and reverse-phase HPLC showed that the major immunoreactivity corresponded to rat proANP. The semipurified irANP of egg extracts produced a dose-dependent relaxation on rat aortic strips, which was blocked by preincubation with anti-ANP antiserum. Therefore, we suggest that ANP is synthesized in the silkworm egg.

Frog lymph heart synthesizes and stores immunoreactive atrial natriuretic peptide

The presence of immunoreactive atrial natriuretic peptide (irANP) and ANP gene expression in the frog lymph heart was examined by a radioimmunoassay (RIA) combined with HPLC and by Northern blot hybridization of total RNA. Serial dilution curve of the lymph heart extract was paralleled with the RIA standard curve. The lymph heart contained 153.32 +/- 35.80 pg of irANP/mg of wet tissue. The major form of irANP in the frog lymph heart was high molecular weight on reverse-phase and gel permeation high performance liquid chromatography as in the frog atria and ventricles. The frog lymph heart, as well as frog atria and ventricles, was shown to express mRNA coding for ANP. Dense core secretory granules similar to those observed in the mammalian atria were also found in the frog lymph heart. The presence of irANP and the expression of ANP gene in the frog lymph heart suggest that the lymph heart may participate in the regulation of homeostasis of lymph circulation and blood volume change through the synthesis and release of ANP.

Identification of immunoreactive atrial natriuretic peptide in bulbus arteriosus of freshwater teleostean fish

1. The presence and partial characterization of immunoreactive atrial natriuretic peptide (ir-ANP) in the bulbus arteriosus were investigated using high performance liquid chromatography (HPLC) and radioimmunoassay (RIA) in several freshwater teleostean fish (catfish, silver crusian carp, snakehead, and rice eel). 2. The level of ir-ANP in the bulbus arteriosus was comparable with that in the atria at about 5-15 pg/mg, 6-13 pg/mg wet wt, respectively, but was 2-4-fold higher than that in the ventricles in all species observed. 3. The HPLC profile of ir-ANP showed two main peaks corresponding to low and high mol. wt rat ANPs. 4. Our results provide evidence for the presence of ir-ANP with high as well as low mol. wts in the bulbus arteriosus of freshwater teleostean fish.

Characterization of angiotensin I-converting enzyme activity in the freshwater turtle, Amyda japonica

1. Angiotensin I-Converting Enzyme (ACE) activity has been characterized in the freshwater turtle, Amyda japonica. 2. Peak activity of ACE in plasma from the freshwater turtle was shown at pH 9.0, which was more alkaline compared to that of mammals. 3. Chloride requirements for the optimal ACE activity were different from species. 4. ACE inhibitors, EDTA, teprotide (SQ 20,881), Captopril (SQ 14,225) showed dose-dependent inhibitions of ACE activity in plasma from the freshwater turtle as well as mammals. 5. ACE activity was found in several different tissues with a different activity showing the highest activity in kidney homogenate from the freshwater turtle, Amyda japonica.