Regulation of SERCA Ca2+ pump expression by cytoplasmic Ca2+ in vascular smooth muscle cells

Vascular smooth muscle cells (VSMC) express three isoforms of the sarcoplasmic or endoplasmic reticulum Ca2+-ATPase (SERCA) pump; SERCA2b predominates (91%), whereas SERCA2a (6%) and SERCA3 (3%) are present in much smaller amounts. Treatment with thapsigargin (Tg) or A-23187 increased the level of mRNA encoding SERCA2b four- to fivefold; SERCA3 increased about 10-fold, whereas SERCA2a was unchanged. Ca2+ chelation prevented the Tg-induced SERCA2b increase, whereas Ca2+ elevation itself increased SERCA2b expression. These responses were discordant with those of 78-kDa glucose-regulated protein/immunoglobulin-binding protein (grp78/BiP), an endoplasmic reticulum stress-response protein. SERCA2b mRNA elevation was much larger than could be accounted for by the observed increase in message stability. The induction of SERCA2b by Tg did not require protein synthesis, nor was it affected by inhibitors of calcineurin, protein kinase C, Ca2+/calmodulin-dependent protein kinase, or tyrosine protein kinases. Treatment with the nonselective protein kinase inhibitor H-7 prevented Tg-induced SERCA2b expression from occurring, whereas another nonselective inhibitor, staurosporine, was without effect. We conclude that changes in cytosolic Ca2+ control the expression of SERCA2b in VSMC via a mechanism involving a currently uncharacterized, H-7-sensitive but staurosporine-insensitive, protein kinase.

Systemic lupus erythematosus and peritoneal dialysis: outcomes and infectious complications

OBJECTIVE

Systemic lupus erythematosus (SLE) is the most common secondary glomerulonephritis resulting in end-stage renal disease (ESRD) among young adults in Taiwan. Studies of the infectious complications and outcomes among such SLE patients undergoing peritoneal dialysis (PD) are limited.

DESIGN

A retrospective age- and gender-matched case control study.

SETTING

A university teaching hospital.

PATIENTS

There were 23 SLE patients with ESRD receiving PD for more than 3 months during the past 15 years. Another 46 age- and gender-matched non-SLE nondiabetic patients receiving PD were selected as the control group in this study.

INTERVENTION

All patients underwent PD as renal replacement therapy and were regularly followed up at this hospital.

MAIN OUTCOME MEASURES

Technique survival and incidences of exit-site infection (ESI) and peritonitis in these patients.

RESULTS

The SLE patients had a lower predialysis serum albumin than the control group (3.16 +/- 0.50 g/dL vs 3.52 +/- 0.50 g/dL, p < 0.01). The incidences of exit-site infection (ESI) and peritonitis were higher for SLE patients than for control patients (p < 0.01 and p < 0.001, respectively). Kaplan-Meier survival analysis indicated that SLE patients had shorter time intervals to first infectious complications, and poorer technique survival. Infection was the major cause of dropout and mortality in the SLE patients. The SLE patients had a reduced chance of receiving a renal transplant. The use of steroids by SLE patients was associated with a higher incidence of peritonitis (p = 0.04), but association with ESI was insignificant. In a Cox regression model, the underlying SLE was the only risk factor for technique failure and time interval to first infectious complication.

CONCLUSION

SLE patients undergoing PD are more susceptible to infection than age- and gender-matched non-SLE nondiabetic patients and have poorer technique survival. Systemic lupus erythematosus itself may further compromise the immunity of uremic patients.

Comparison of infectious complications in peritoneal dialysis patients using either a twin-bag system or automated peritoneal dialysis

BACKGROUND

Automated peritoneal dialysis (APD) and twin-bag (TB) systems are two major peritoneal dialysis (PD) modalities. Published data comparing the infectious complications of these modalities is limited. Subjects and methods. Ninety-five patients using APD (the APD group) and 117 patients using TB system (the TB group) were recruited. Among them, 35 patients used both modalities. The two groups' clinical characteristics, incidences of infectious complications, and the time intervals to first PD-related infection were compared.

RESULTS

Clinical characteristics, incidence of exit-site infection (ESI), and time intervals to first ESI were similar in the TB and APD groups. The incidence of peritonitis in the APD group (1.22 episodes/100 patient-months) was significantly (P < 0.001) lower than that of the TB group (2.28 episodes/100 patient-months). Using the Cox proportional hazard model, APD was found to have a lower risk of peritonitis relative to TB systems, with marginal significance (RR 0.58, P = 0.051).

CONCLUSION

APD was found to have a lower peritonitis rate than the TB system. Since reducing the peritonitis rate helps to maintain technical survival during PD, from this viewpoint, APD may be preferred for patients undergoing PD, unless contraindicated.

Incidence of exit-site infection with various exchange systems in continuous ambulatory peritoneal dialysis

BACKGROUND AND PURPOSE

The disconnect twin-bag (TB) system was first introduced in Taiwan for use as an exchange system in continuous ambulatory peritoneal dialysis (CAPD) in 1995. Following its introduction, the incidence of CAPD-associated peritonitis declined, but the incidence of exit-site infection (ESI) increased. To determine the cause of the increase in ESI incidence after the introduction of the TB system, this study compared the incidence of ESI among patients using the O set, ultraviolet antiseptic (UV) device, and the TB system.

METHODS

A total of 170 patients who had received CAPD for more than 3 months were enrolled in this study. Poisson test and Kaplan-Meier survival analysis were used to compare the ESI incidence and ESI-free catheter survival among patients using the O set, UV device, or TB system. Cox stepwise forward proportional hazard analysis was used to assess the impact of sex, education, cause of uremia, age, and type of exchange system on ESI.

RESULTS

The incidences of ESI differed significantly among patients using the three exchange systems, with 20.9, 13.8, and 4.0 episodes per 100 patient-years for patients using the TB system, O set, and UV device, respectively. New patients using the TB system also had a shorter mean interval of ESI-free catheter survival than those using the UV device (26.9 vs 58.8 months, p = 0.002). In the Cox stepwise forward proportional hazard analysis, non-lupus patients had a lower risk of developing ESI than lupus patients (relative risk [RR] 0.40, p = 0.03). The RR of ESI in patients using the UV device was also lower than in those using the TB system (RR 0.15, p < 0.01).

CONCLUSION

In this study, use of the TB system was associated with a higher incidence of ESI. The increased ESI incidence may be related to the heavier mini-transfer set of the TB system. Therefore, special attention should be given to fastening the mini-transfer set tightly during the exchanging procedure to prevent traction on the exit-site, which is associated with an increased incidence of subsequent ESI.

Expression pattern in a modified equalized kidney cDNA library of hypertensive rat

BACKGROUND

Genes with important functions and rarely expressed would probably more easily be cloned from a modified equalized kidney cDNA library for further investigation.

METHODS

A kidney cDNA library of a spontaneously hypertensive rat was synthesized by a modified equalization method. Inserts of random clones were amplified by PCR and sequenced. Sequences were compared against a nonredundant database in GenBank. The cDNA profile was compared with an expression profile of a mouse renal proximal tubule cDNA library. Seven clones were analyzed by Northern blot analysis. The cDNA ends of two novel genes were amplified by PCR, sequenced and analyzed.

RESULTS

336 cDNA clones were analyzed and grouped into 323 species of transcript with 77 species similar to previously reported genes. Northern blot analysis identified one kidney-specific, one rarely expressed and lung-specific, and another relatively testis-specific gene. Two novel genes were cloned. One was 4.1 kb in length and encoded a 390-amino acid zinc-finger protein. Another was 2.5 kb and encoded a 474-amino acid protein of unknown function. Compared with the expression profile of a mouse renal proximal tubule cDNA library, this kidney library had a lower proportion of ribosomal genes and had a greater proportion of genes for signal transduction and DNA or RNA binding.

CONCLUSIONS

Rare or novel genes could be more easily isolated from this library for molecular study of hypertension and renal pathophysiology.

Clinical features of and risk factors for fungal peritonitis in peritoneal dialysis patients

BACKGROUND AND PURPOSE

Fungal peritonitis (FP) is a serious complication for peritoneal dialysis (PD) patients and can result in technical failure and mortality. Catheter removal remains the mainstay of treatment. This study sought to identify the risk factors for FP in order to facilitate the prevention of this catastrophic complication.

METHODS

A total of 246 patients who received long-term PD from 1985 to 1998 were included in this retrospective study. Twenty episodes of FP occurred in 19 patients. The clinical characteristics, pathogens, treatment modalities, and outcomes of the FP episodes were retrospectively reviewed. The FP incidence in various demographic and clinical groups, classified according to sex, age, education, and underlying cause of uremia, were compared with the Poisson test.

RESULTS

Thirteen episodes of FP were caused by yeast, and the remaining episodes were caused by Aspergillus spp. Age, sex, and education did not affect the FP incidence. Lupus patients (969 patient-months) had a higher incidence of FP than patients with other underlying diseases (p < 0.05). The 19 FP patients also had a higher incidence of bacterial peritonitis than other PD patients (p < 0.01). Among the 20 FP episodes, 14 (70%) were preceded by antibiotic use, and eight (40%) developed during hospitalization. Steroids were used at the time of FP in five of six lupus patients. Seven patients (37%) died within 1 month after diagnosis of FP. Five patients were able to remain on PD after FP, but only three patients were able to maintain catheter placement.

CONCLUSION

The risk factors for FP identified in this study include the use of antibiotics and steroids, underlying lupus, frequent occurrence of bacterial peritonitis, and hospitalization. Antifungal therapy may allow the catheter to be kept in place in a few patients, but catheter removal should be considered in patients whose FP is refractory to medical treatment.

Lack of evidence for an association between alpha-adducin and blood pressure regulation in Asian populations

Recent studies have found the tryptophan allele of a glycine to tryptophan polymorphism at position 460 (G460W) of the alpha-adducin protein to be associated with essential hypertension in European populations. We examined whether the tryptophan allele is associated with hypertension in a different population, comprised of subjects of Chinese origin from Taiwan, and Chinese and Japanese origin from the San Francisco Bay area and Hawaii. We adapted the 5' allelic discrimination assay or TaqMan to type individuals for the G460W polymorphism, and using this method we typed more than 1000 individuals. The frequency of the W allele was slightly increased in the treated subjects in the Chinese population (0.458 v 0.423) but not the Japanese population (0.549 v 0.558). We considered dominant, recessive, and additive models in our analysis. There was a significant result for a recessive model for systolic blood pressure in the Chinese population (chi2 6.84, df = 2, P < .05), but only suggestive evidence for diastolic blood pressure (chi2 3.30). In contrast, in the Japanese population, there was no evidence for a positive association under any model. For the combined Chinese and Japanese samples, the evidence for association with alpha-adducin was not significant.

Endothelin-1 chronically inhibits Na/H exchanger-3 in ET(B)-overexpressing OKP cells

Endothelin-1 (ET-1) acutely increases Na/H antiporter activity in OKPET(B)6 cells, an opossum kidney proximal tubule cell line transfected with ET(B) receptor cDNA. The purpose of the present study was to examine the chronic effect of ET-1 on Na/H antiporter activity in OKP cells and to examine whether Na/H exchanger (NHE)-3 mRNA and protein abundance are regulated by ET-1. Quiescent OKPET(B)6 cells were treated with 10 nM ET-1 for 3, 6 or 24 h and Na/H antiporter activity was assayed. The Na/H antiporter activity in 3-h ET-1-treated cells was not different from controls. However, Na/H antiporter activity was significantly decreased by 29% at 6 h and 72% at 24 h. The effect of ET-1 on Na/H antiporter activity was blocked by BQ788, an ET(B) receptor antagonist, but not BQ123, an ET(A) receptor antagonist. The NHE-3 mRNA abundance in ET-1-treated cells was not different from controls at 3 h. However, there was a significant decrease in NHE-3 mRNA abundance at 6 and 24 h. There was also a significant decrease in NHE-3 protein abundance at 6 and 24 h. In summary, ET-1 chronically inhibits NHE-3 in OKPET(B)6 cells.

Pentoxifylline attenuates experimental mesangial proliferative glomerulonephritis

BACKGROUND

Accumulation of glomerular macrophages, proliferation of mesangial cells (MCs), and deposition of extracellular matrix proteins are pathobiological hallmarks of glomerulonephritis. We previously reported that a clinically available nonselective inhibitor of cyclic 3',5'-nucleotide phosphodiesterase, pentoxifylline (PTX), inhibits proliferation of cultured rat MCs, as well as collagen production by these cells. In this study, we investigated the in vivo effects of PTX on rat anti-Thy1 disease, a model of mesangial proliferative nephritis.

METHODS

Anti-Thy1 nephritis was induced in Sprague-Dawley rats by injecting mouse anti-rat Thy1 antibodies intravenously. Nephritic rats were randomly assigned to receive PTX (0.1 g/kg/day) or vehicle (phosphate-buffered saline) and were sacrificed at various time points. Paraffin kidney sections were stained with hematoxylin and periodic acid-Schiff reagents for glomerular histology. Frozen kidney sections were stained by monoclonal antibodies against proliferating cell nuclear antigen, ED-1, and alpha-smooth muscle actin and were visualized by color development from a horseradish peroxidase reaction. Monocyte chemoattractant protein-1 (MCP-1), intercellular adhesion molecule-1 (ICAM-1), and various extracellular matrix mRNAs were analyzed by Northern blotting. Urine protein concentrations were determined by Lowry's method.

RESULTS

Nephritic rats treated with PTX excreted less urinary protein on day 5 of nephritis than vehicle-treated nephritic rats. In periodic acid-Schiff-stained kidneys from PTX-treated nephritic rats, there was attenuation of both glomerular cellularity and glomerular sclerosis compared with vehicle-treated nephritic rats. PTX decreased the augmented glomerular mRNA levels of MCP-1 and ICAM-1 at two hours and on day 1 of nephritis. Immunoreactive staining showed that PTX reduced the number of proliferating glomerular macrophages on days 1, 2, and 3, but not at two hours of nephritis, compared with vehicle-treated nephritic rats. On day 5, PTX decreased the number of activated proliferating MCs and attenuated the glomerular mRNA levels of type I (alpha1), type III (alpha1), and type IV (alpha1) collagen and fibronectin compared with vehicle-treated nephritic rats.

CONCLUSION

The administration of PTX to rats with anti-Thy1 disease reduces accumulation and proliferation of glomerular macrophages, attenuates proteinuria, suppresses activation and proliferation of MCs, and ameliorates glomerular sclerosis. These results suggest that PTX may have a suppressive effect in acute phases or relapses of mesangial proliferative glomerulonephritis.

Differential expression of type 1 angiotensin II receptor mRNA and aldosterone responsiveness to angiotensin in aldosterone-producing adenoma

Aldosterone secretion in most patients with aldosterone-producing adenomas (APAs) is typically unresponsive to angiotensin II stimulation (AII-unresponsive, AII-U). In some patients, however, plasma aldosterone increases in response to AII stimulation (AII-responsive, AII-R). This differential aldosterone responsiveness could be related to the levels of type 1 AII receptors (AT1R) in the APA. To test this hypothesis, plasma aldosterone levels in response to upright posture and/or sequential high- and low-salt diets were measured by radioimmunoassay in nine patients with APAs. AT1R mRNA levels in the adenomas were quantified by competitive reverse transcription-polymerase chain reaction and correlated to the cellular composition of the adenoma. Two patients were categorised as AII-R by an increase of plasma aldosterone greater than 50% over the baseline. The remaining seven patients who had blunted plasma aldosterone responses were classified as AII-U. Histologically, the AII-R APAs consisted predominantly of zona glomerulosa (ZG)-like cells (> 90%), while the AII-U APAs contained zona fasciculata (ZF)-like cells ranging from 28 to 72%. There was an inverse relationship between the levels of AT1R mRNA in the APA and the percentage of ZF-like cells in the adenoma (n = 9, r = 0.73, P < 0.05). In situ hybridisation findings demonstrated that AT1R mRNA was more uniform and intensive in ZG-like cells than in ZF-like cells. These results suggest that heterogenous aldosterone responsiveness to angiotensin in APAs is histologically dependent and related to the differential expression of AT1R mRNA in the adenoma.

Pentoxifylline inhibits PDGF-induced proliferation of and TGF-beta-stimulated collagen synthesis by vascular smooth muscle cells

There is growing evidence that pentoxifylline (PTX) may have potential value as an antiproliferative and antifibrogenic agent. To assess whether this drug may be of use in the prevention of atherosclerosis or restenosis after angioplasty, we investigated the ability of PTX to inhibit proliferation and collagen synthesis in rat vascular smooth muscle cells (VSMCs) under both basal and platelet-derived growth factor (PDGF)- or transforming growth factor-beta (TGF-beta)- stimulated conditions. Intracellular cyclic AMP (cAMP) and cyclic GMP (cGMP) levels were measured in confluent cells using enzyme immunoassay kits. Cell proliferation was measured by methyltetrazolium assay. Cell cycle distribution was determined by flow cytometry. Total collagen synthesis was measured by 3H-proline incorporation assay. Expression of collagen alpha 1(I) and collagen alpha 1(III) mRNAs was detected by northern blotting. Addition of PTX to VSMC cultures suppressed both basal and PDGF-AB (25 ng/ml)-driven cell proliferation, in conjunction with a cell cycle blockade at the G1/S phase at 24 h. This effect was predominantly cAMP-dependent, as PTX increased cAMP in a dose-dependent manner (0.03 to 0.33 mg/ml) but not cGMP level, and the addition of dibutyryl-cAMP (0.2 to 2 m m) closely mimicked the effect of PTX. Furthermore, co-incubation with a selective inhibitor of cAMP-dependent protein kinase (PKA), H-89 (2.0 microm), or an N -myristoylated PKA pseudosubstrate nonapeptide, m-phi PKA (10 microm), prevented the antimitogenic effect of PTX. PTX also suppressed both basal and TGF- beta 1-augmented collagen alpha 1(I) and collagen alpha 1(III) mRNA levels beginning at 24 h, and attenuated both basal and TGF-beta 1 (5 ng/ml)-stimulated total collagen synthesis at 48 h. Co-incubation with H-89 or m-phi PKA reversed PTX-attenuated collagen alpha 1(I) and collagen alpha 1(III) mRNA levels at 24 h. These data suggest that the antimotigenic and anticollagen effects of PTX were mediated predominantly through a cAMP-PKA effector pathway. The dual effect of PTX on VSMC proliferation and collagen synthesis may form the rationale for animal or clinical trials for the treatment of vascular occlusion due to atherosclerosis and restenosis following angioplasty.

Low back pain in college athletes. A prospective study correlating lower extremity overuse or acquired ligamentous laxity with low back pain

STUDY DESIGN

A prospective evaluation of the incidence of low back pain in college athletes was undertaken.

OBJECTIVES

To evaluate prospectively leg length discrepancy, hip flexor tightness, and lower extremity acquired laxity or overuse as predictive factors for low back pain in college athletes.

SUMMARY OF BACKGROUND DATA

A pilot study found an association between low back pain and the factors to be studied. Several allusions to the kinetic chain theory appear in the literature, but little prospective research has been done in examining the effects of lower extremity involvement on the back.

METHODS

Two-hundred fifty-seven college athletes representing nine varsity sports were screened during a preseason sports physical examination. Measures of flexibility, ligamentous stability, leg length discrepancy, and overuse syndromes were recorded. Athletes were observed throughout the ensuing year for low back pain requiring treatment by the athletic trainer. Those athletes with low back pain as the result of direct trauma to the region were excluded from the data.

RESULTS

Twenty-four athletes (9.3%) received treatment for low back pain. Thirteen of 87 women (15%) compared with 11 of 170 men (6%) required treatment for low back pain (P = 0.048). Of 57 athletes with lower extremity acquired laxity or overuse, low back pain developed in 14 (P < 0.001).

CONCLUSIONS

Athletes with lower extremity acquired ligamentous laxity or overuse may be at risk for the development of noncontact low back pain during athletic competition. Female athletes with lower extremity involvement appeared to have a higher incidence of low back pain treatment compared with their male counterparts. Inflexibility of the lower extremities or leg length discrepancy were not associated with future low back pain treatment.

Extracellular matrix proteins modulate human peritoneal mesothelial cell behavior

Human peritoneal mesothelial cells lie on a basement membrane-like material consisting of fibronectin (FN), type I collagen (CI), type III collagen (CIII) and laminin (LA). To understand how these extracellular matrix (ECM) proteins affect mesothelial cell behavior, we investigated their effect on the adhesion and proliferation of mesothelial cells. A modified methyltetrazolium dye method was used to assess cell number. The results showed that FN, CI, CIII and LA, all increased adhesion of mesothelial cells. The adhesive effect was blocked dose-dependently by a synthetic Arg-Gly-Asp-containing (RGD) peptide. When coated as a substratum (immobilized form), FN, CI, CIII and LA, all enhanced serum-stimulated and epidermal-growth-factor-stimulated cellular proliferation as compared with bovine-serum-albumin-blocked plastic surfaces. When added in a soluble form, all matrix proteins except FN inhibited serum-stimulated and epidermal-growth-factor-stimulated cellular proliferation at high concentrations (CI and CIII: 1-10 micrograms/ml, LA: 3-10 micrograms/ml). We conclude that peritoneal mesothelial cells possess an RGD-sensitive receptor and that the ECM can modulate adhesion and proliferation of peritoneal mesothelial cells. The growth-modulating effect depends on the form and concentration of the ECM proteins.

Revised cutoff values of serum aminotransferase in detecting viral hepatitis among CAPD patients: experience from Taiwan, an endemic area for hepatitis B

BACKGROUND

To determine the best cutoff values of aspartate aminotransferase (AST) and alanine amino-transferase (ALT) in detecting viral hepatitis C infection among patients of continuous ambulatory peritoneal dialysis (CAPD).

METHODS

90 (44 male and 46 female) CAPD patients and 526 adult controls (266 male, 260 female) were enrolled. Serum AST and ALT were measured by an auto-analyser monthly. Serum HBsAg was examined using a RIA method and anti-HCV by an second-generation EIA method. The best cutoff values of AST and ALT for detecting viral hepatitis were obtained from the ROC (receiver-operating characteristic) curve.

RESULTS

The prevalence of anti-HCV(+) was significantly higher in CAPD patients (16.7%) than in normal controls (4.9%), while that of HBsAg(+) was similar in both groups. CAPD patients had significantly lower levels of serum aminotransferases compared to normal controls. Mean AST were 23.8 IU/l in normal control and 18.8 IU/l in the CAPD patients (P < 0.001). Mean ALT were 21.9 IU/l in normal controls and 15.3 IU/l in the CAPD patients (P < 0.001). CAPD patients with HCV infection had higher serum AST and ALT levels than those without. However, HBV infection did not cause significant serum aminotransferase elevation in patients. The conventional cutoff values of AST (40 IU/l) and ALT (40 IU/l) for detecting viral hepatitis yielded only a sensitivity of 27.3 and 18.2% respectively; on the contrary, our revised cutoff values of AST (24 IU/l) and ALT (17 IU/l) had better sensitivities (AST, 72.7%; ALT, 63.6%). For serial aminotransferase values, the sensitivity of AST and ALT for detecting HCV were 36.4 and 27.3% by conventional criteria, and were both 81.8%, by our newly revised criteria.

CONCLUSIONS

Serum aminotransferase cutoff values should be modified for screening viral hepatitis in a CAPD population. Our new cutoff criteria had important clinical implications in providing benefits of earlier detection and possible prevention from chronic hepatic deteriorations.

The milk-alkali syndrome caused by betelnuts in oyster shell paste

BACKGROUND

The carcinogenic effect of betelnut chewing leading to oral cancer is well known. Betelnut chewing may also affect the autonomic nervous system. In this report, we present another potential hazard of betelnuts, milk-alkali syndrome.

CASE REPORT

Two patients who had chewed a large quantity of betelnuts developed hypercalcemia, metabolic alkalosis, and renal insufficiency. They ingested a large amount of calcium carbonate from a local special paste used for betelnut preparation, the main ingredient of which is ground oyster shell. The symptoms and metabolic abnormalities disappeared promptly after abstinence from betelnut chewing and administration of saline solution. Improvement of renal function was observed in both patients. Analysis of the calcium content of the paste suggested that the patients might have ingested 9 g and 6 g of calcium carbonate per day, respectively.

CONCLUSION

This is the first report of milk-alkali syndrome not caused iatrogenically, but by recreational usage of oyster shell preparations of betelnuts.

Localization and quantification of endoplasmic reticulum Ca(2+)-ATPase isoform transcripts

The Ca(2+)-adenosinetriphosphatase pump of the sarcoplasmic or endoplasmic reticulum (SERCA) plays a critical role in Ca2+ signaling and homeostasis in all cells and is encoded by a family of homologous and alternatively spliced genes. To understand more clearly the role the different isoforms play in cell physiology, we have undertaken a quantitative and qualitative assessment of the tissue distribution of transcripts encoding each SERCA isoform. SERCA1 expression is restricted to fast-twitch striated muscles, SERCA2a to cardiac and slow-twitch striated muscles, whereas SERCA2b is ubiquitously expressed. SERCA3 is expressed most abundantly in large and small intestine, thymus, and cerebellum and at lower levels in spleen, lymph node, and lung. In situ hybridization analyses revealed SERCA3 transcripts in cells of the intestinal crypt, the thymic cortex, and Purkinje cells in cerebellum. In addition, SERCA3 was expressed abundantly in isolated rat spleen lymphocytes, in various murine lymphoid cell lines, and in primary cultured microvascular endothelial cells. This analysis demonstrates that SERCA3 is expressed selectively in cells in which Ca2+ signaling plays a critical and sensitive role in regulating physiological processes.

Quantitative analysis of messenger ribonucleic acid encoding natriuretic peptide receptors in aldosterone-producing adenoma

There exist conflicting data regarding the inhibitory effect of atrial natriuretic peptide on aldosterone production from aldosterone-producing adenoma (APA). Natriuretic peptides mediate their actions through natriuretic peptide receptors (NPRs). Whether or not NPRs are present in the tumors remains controversial. To elucidate this paradox, gene expression of NPRs was examined by Northern blot analysis and competitive polymerase chain reaction in tumorous and non-tumorous portions of APA, and in normal adrenal gland from patients with renal cell carcinoma. The results of Northern blot analysis showed the presence of messenger ribonucleic acid (mRNA) of three NPRs in all adrenal tissues, including APA. The proportional expression of NPR gene transcripts in APA was type A (0.6%), type B (18.7%), and type C (80.7%). The levels, but not the proportions, of type C and possibly type B NPR mRNAs were lower in tumorous and non-tumorous portions of APA compared to those in normal adrenal gland (type C 190.2 +/- 24.5 [means +/- SEM, normal adrenal gland] > 168.1 +/- 20.8 [non-tumorous portion] > 112.2 +/- 15.5 [tumorous portion] pg/10 micrograms total RNA, F = 3.82, P < 0.05; type B 45.2 +/- 8.5 [normal adrenal gland] > 30.0 +/- 5.2 [non-tumorous portion] > 25.1 +/- 4.1 [tumorous portion] pg/10 micrograms total RNA, F = 3.03, P = 0.065). The mRNA levels of type C, rather than type A or type B, NPR were correlated with the percentage of zona fasciculata-like cells in APA (r = 0.90, P < 0.05). In conclusion we have demonstrated the presence of mRNA encoding the three NPRs in APA.(ABSTRACT TRUNCATED AT 250 WORDS)

Diagnostic value of plasma aldosterone/potassium ratio in hypoaldosteronism

The diagnosis of hypoaldosteronism usually depends upon a combination of abnormal clinical and laboratory findings. The most common abnormality in hypoaldosteronism is hyperkalemia, which may be combined with sodium depletion. In the present study, 5 of 16 patients diagnosed with isolated hypoaldosteronism (IHA) had sodium depletion due to renal salt wasting, and four patients had normokalemia. Of these 16 IHA patients, 70% had subnormal baseline and stimulated plasma renin activity (PRA). Six patients diagnosed with type I pseudohypoaldosteronism (PHA) had normal or high PRA and plasma aldosterone concentrations (PAC). In 11 control subjects, supine PAC correlated positively with serum potassium (SK), and PAC stimulated by furosemide and ambulation correlated with the 24-hour urinary potassium excretion (UK). However, these correlations were not found in IHA and PHA patients. The ratio of UK/UNa+K and UNa/UK correlated with the stimulated PAC when the IHA and control subjects were taken as a whole. However, these electrolyte excretion parameters bore no relationship to the supine PAC. The stimulated PAC/SK ratio was used to discriminate the three groups; all IHA patients had a ratio below 3. The results indicate that stimulated PAC reflects the bioactivity of aldosterone on the collecting tubule, and the stimulated PAC/SK ratio is useful for the diagnosis of hypoaldosteronism and pseudohypoaldosteronism.

Zona fasciculata-like cells determine the response of plasma aldosterone to metoclopramide and aldosterone synthase messenger ribonucleic acid level in aldosterone-producing adenoma

The different responses of plasma aldosterone to ACTH and angiotensin II in aldosterone-producing adenoma (APA) is thought to be due to the various cellular compositions of the tumors. To investigate whether the dopaminergic regulation of aldosterone in APA is also dependent on the cellular types, we studied the effects of metoclopramide on plasma aldosterone in six patients with APA. The messenger RNA (mRNA) levels of aldosterone synthase (P450aldo), 11 beta-hydroxylase (P450(11) beta), and 17 alpha-hydroxylase (P450(17) alpha) of APA and normal adrenal glands were determined by competitive polymerase chain reaction. After administration of metoclopramide (an antagonist of dopamine-2 receptor), the increment of plasma aldosterone correlated inversely with the percentage of zona fasciculata cells of APA. The mRNA level of P450aldo in the tumorous portion was much higher, whereas the levels of P450(11) beta and P450(17) alpha mRNAs were lower, than those of the nontumorous portion and normal adrenals. There was a correlation of the percentage of zona fasciculata cells in APA with the levels of P450aldo and P450(11) beta mRNAs, but not with P450(17) alpha mRNA. These results suggest that differential responsiveness of plasma aldosterone to metoclopramide may be due to various proportions of different cell types in APA that may have different expression of dopamine-2 receptor. In addition, this histologically dependent expression was present at the transcriptional level of the gene responsible for aldosterone biosynthesis.

Blood pressure, circulating atrial natriuretic peptide and sodium excretion responses during acute saline infusion in patients with essential hypertension

In order to examine whether changes in circulating atrial natriuretic peptide (ANP) and sodium excretion during saline infusion in patients with essential hypertension (EH) could be modulated by the severity of resting arterial blood pressure (BP), 30 subjects with EH and nine normotensive subjects were given 2 L of isotonic saline infusion at a rate of 500 mL/hour. Plasma ANP concentrations in EH increased significantly from 64.9 +/- 5.1 (mean +/- SEM) to 92.5 +/- 12.8 pg/mL at the first hour and peaked at the second hour. In normotensives, the increase of plasma ANP was not significant until the fourth hour of infusion. Hypertensive subjects sustained a greater percentage increment of mean BP (MBP) than normotensives at the end of infusion. Those with pre-saline MBP exceeding 107 mmHg (group A) exhibited a faster and greater rise in plasma ANP after saline loading than those having less than or equal to 107 mmHg (group B). The post-saline four-hour natriuresis was appreciably higher in group A than group B, while the percentage increment of MBP at the fourth hour was significantly greater in the latter as compared to normal controls. These results indicate that patients with higher basal arterial pressure attain a faster and greater ANP response following saline infusion than those with lower BP. This phenomenon may be responsible for the maintenance of short-term fluid-volume and BP homeostasis during acute sodium loading in established EH.

Blood pressure response to angiotensin converting enzyme inhibitor in essential hypertension: its relation to the renin status and natriuresis during acute sodium loading

We examined the antihypertensive response to enalapril and its relation to the changes of the renin-angiotensin-aldosterone axis (RAA) in essential hypertensive patients. The responders, whose blood pressure reduced after enalapril administration, had significant elevation of plasma renin activity after enalapril (7.5 +/- 4.0 to 31.9 +/- 10 ng/mL/h, p < 0.05). There was no significant change in the plasma renin activity of the nonresponders (3.0 +/- 1.0 to 5.6 +/- 1.9 ng/mL/h). Natriuretic response to acute salt loading was compared between the two subgroups. The natriuresis on acute salt loading of nonresponders was better than that of the responders (82.9 +/- 13.2 vs 44.5 +/- 5.7 mmol/4h, p < 0.05). These results imply that the RAA and extracellular fluid volume both contribute in different ways to the maintenance of high blood pressure in different subgroups of essential hypertension.

Heterogeneous blood pressure response to furosemide and captopril in primary aldosteronism

The hypertension associated with primary aldosteronism (PA) is often regarded as volume dependent/salt-sensitive. However, not all patients sustain an increase in blood pressure upon sodium loading. In order to examine the sodium sensitivity in PA, 21 patients with aldosteronoma were tested for acute hypotensive response to intravenous furosemide and oral captopril. Ten patients having a decrease in mean blood pressure (MBP) exceeding 5% at the second hour after a 20 mg furosemide injection were defined as diuretic-responders (DR), while the remainder were defined as diuretic-non-responders (DN). The DR group had a higher baseline MBP (135 +/- 6 [mean +/- SE] vs 121 +/- 4 mmHg, p < 0.05) and serum sodium concentration (145.7 +/- 1.4 vs 143.0 +/- 0.7 mmol/L, p < 0.05) than the DN group. The extent of natriuresis induced by furosemide was not different between the two subgroups. Following 100 mg of captopril administered orally, the DR group had a smaller change in MBP (%) than the DN group (3.08 +/- 5.14 vs -7.78 +/- 3.37, p < 0.05). According to the different BP responses to furosemide and captopril, we conclude that PA patients may be further divided into DR and DN. The DR group had a good response to diuretics whereas the DN group responded better to converting enzyme inhibitors. This classification of PA in terms of blood pressure response to furosemide may have therapeutic implications.