The gonadotrope polypeptide (GP 87) released from pituitary cells under luteinizing hormone-releasing hormone stimulation is a secretogranin II form.

Cultured gonadotrope cells from 14 day old female rat pituitaries have been shown to release a highly acidic protein when incubated with LHRH: the gonadotrope polypeptide (GP 87). Moreover, a new tyrosine-sulfated acidic protein, secretogranin II (Sg II), clearly distinct from the chromogranin species, was described in the secretory granule matrix of endocrine cells secreting peptide hormones by the regulated pathway. Recently, the release of Sg II from female rat pituitary stimulated by LHRH was demonstrated in vitro. Several physicochemical (Mr; pI) and biological (cellular localization in the pituitary; LHRH-stimulated release) properties are common to Sg II and GP 87. To verify if these 2 polypeptides are similar or distinct components, other physicochemical characteristics (heat-stability, sulfation, phosphorylation) were compared using isotope incorporation followed by either 1- or 2-dimensional polyacrylamide gel electrophoresis and autoradiography. Furthermore, the similarity of GP 87 to Sg II was studied by immunoblotting on nitrocellulose sheets following electrophoresis of intracellular and secreted proteins. Antisera raised against bovine Sg II (extracted from whole pituitaries) and against rat GP 87 (released into the medium of cultured pituitary cells stimulated by LHRH) were used. The overall data presented here suggest that GP 87 is the Sg II form contained in, and released by, gonadotrope cells.

Immunohistochemical localization of secretogranin II in the rat cerebellum.

Secretogranin II (chromogranin C) is a peptide related to chromogranin A and secretogranin I (chromogranin B) which is secreted by a regulated pathway from both neurons and endocrine cells. In the present study we have determined by light microscopic immunocytochemistry its distribution in the cerebellum and in adjacent brain stem regions. Secretogranin II was found to be widely distributed throughout the gray matter of these regions. Highly immunoreactive structures in the cerebellar cortex included the majority of climbing fibers, a large number of mossy fibers, sparse varicose fibers in the molecular layer and a subpopulation of neuronal perikarya in the granule cell layer. The location and shape of these neurons are very similar to those of a novel type of cerebellar neurons which has been recently described. A moderate level of immunoreactivity was observed on fibers travelling among Purkinje cells and parallel to the pial surface in the Purkinje cell layer. A variable, but in general low, degree of immunoreactivity was also detectable in the perikarya of Purkinje cells. In the deep cerebellar nuclei a loose network of secretogranin II-positive fibers was visible. Neurons of the nuclei, however, were non-immunoreactive. A dense network of highly immunoreactive fibers was found throughout the brain stem regions adjacent to the cerebellum. Our results indicate that secretogranin II has in the cerebellum and adjacent regions a distribution more widespread than that of known regulatory peptides and suggest that the peptide-mediated signaling in the cerebellum plays a role more important that has been acknowledged so far.

Sulfated LH subunits and a tyrosine-sulfated secretory protein (secretogranin II) in female rat adenohypophyses: changes with age and stimulation of release by LHRH.

Sulfated proteins are present in adenohypophyseal secretory granules but their function and structure are still largely unknown. We studied these proteins in homogenates from cow and rat adenohypophyses labeled in vitro with [35S]sulfate, by one-dimensional and two-dimensional polyacrylamide gel electrophoresis followed by fluorography. We found that the heterogeneous neutral-alkaline sulfated components of approximately 22-20 kDa and approximately 20-18 kDa previously described correspond to lutropin alpha and beta subunits sulfated on carbohydrates. During development sulfated lutropin subunits were found at highest levels in anterior pituitary glands of 14-day-old female rats. Secretogranin II, an acidic tyrosine-sulfated secretory protein, whose presence in granules of gonadotrophs has been recently described, had a similar distribution during development. In the 14-day-old female rat glands luteinizing hormone-releasing hormone stimulated the in vitro release of both sulfated lutropin subunits and secretogranin II. This finding further suggests that secretogranin II might be involved in the packaging of the gonadotrophin. Immature female rat adenohypophyses provide a useful approach for studying sulfation, both on carbohydrate and on tyrosine residues, of secretory proteins.

Effect of familial hypertension on glomerular hemodynamics and tubulo-glomerular feedback after uninephrectomy.

Familial hypertension, glomerular hemodynamic alterations, and dysregulation of tubulo-glomerular feedback (TGFB) have all been associated with the development of chronic renal failure. In the present study we evaluated renal and glomerular hemodynamics and TGFB responses in healthy kidney donors either with or without familial hypertension, before and after nephrectomy. Para-amino-hippurate plasma clearance (CPAH) and inulin plasma clearance (CInu) were measured in 15 kidney donors before and 1 year after nephrectomy. All subjects were normotensive and were kept in a sodium-replete state. Both clearances were measured after 40 min of constant infusion of PAH and Inu, as well as 20, 30, 50, and 60 min after the intravenous administration of acetazolamide (5 mg/kg). Glomerular hemodynamics were calculated by means of the Gomez formulae. Nephrectomy caused the expected decreases in CPAH and CInu and increase in the filtration fraction (all P < .0001). The decrease in renal resistances of the remaining kidney was greater at the afferent (-24%, P = .0075) than at the efferent arteriolar level (-17%, P < .0001). The TGFB activation was not altered by nephrectomy or by familial hypertension. Effective renal plasma flow (ERPF) decrease after TGFB activation appeared earlier than glomerular filtration rate (GFR) decrease before (P = .01), but not after, nephrectomy (P = .48). The presence of familial hypertension was associated with increased glomerular pressure (P = .0004). This study suggests that uninephrectomy in healthy human subjects causes a greater decrease in afferent arteriolar resistances, but that TGFB responses are not quantitatively altered. Familial hypertension is associated with a tendency toward higher glomerular pressures.

Urinary salt titrator stick: a useful and quick estimate of dietary sodium intake?

Repeated measures of urinary salt excretion are the best compromise between reliability and convenience for estimating dietary salt intake. In order to assess the accuracy of the Uropaper urinary salt titrator stick (giving discrete readings of 4, 6, 8, 10, 12 or 14 g/l of NaCl), 312 urine samples were analysed both with the stick and with an ion-selective electrode. There was a good stick-electrode correlation in all the 312 samples (r = 0.84). With a tolerance of +/- 1 g/l, the percentages of correct estimations dropped from 82% to 33% with increasing concentrations of NaCl in the urinary sample. For NaCl concentrations greater than 8 g/l (137 mmol/l) the error in the stick measurement consisted almost exclusively of overestimation of the electrode readings. These results were unaffected by the concentration of urinary potassium. No discrepancies were found among three different readers. This stick is easy to use and measures, with reasonable accuracy, low urinary NaCl concentrations. It could be useful for self-monitoring during low NaCl diets.

Donor and recipient family histories of hypertension influence renal impairment and blood pressure during acute rejections.

A previous historical prospective observational study, double blinded for knowledge of kidney donors' family history of hypertension, included 85 transplanted patients with stable renal function, not treated with cyclosporine, who were followed-up for an average of 8 yr and carefully characterized for the presence or absence of hypertension in the donor and recipient families. The recipients without a family history of hypertension, but grafted with a kidney coming from a "hypertensive" family, developed hypertension much more frequently than recipients grafted with a kidney coming from a "normotensive" family, or recipients with familial hypertension in whom the origin of the kidney did not influence the prevalence of hypertension after transplantation. In this second study of the same patients, it was found that these recipients with a "normotensive" family and a "hypertensive" kidney showed a greater increase of diastolic BP (P = 0.005) and a greater degree of acute renal damage (P = 0.004) during acute rejections than all of the other recipients. This extension study shows that a grafted kidney can transmit not only chronic hypertension, but also susceptibility to a greater rise in BP and more severe kidney impairment after an acute insult.

Growth hormone-releasing hormone and clonidine stimulate biosynthesis of growth hormone in neonatal pituitaries.

Comparative studies were performed to verify the effect of growth hormone releasing hormone (GHRH) or clonidine (CLON), a compound thought to act via release of endogenous GHRH, in stimulating GH biosynthesis in the pituitary from neonatal and adult rats. In vitro preincubation for 1 h with GHRH (hpGRF-40, 10(-8) M) increased the incorporation of L-[3H]leucine in the electrophoretic band of GH in the pituitary from 10-day-old rats, but not in the gland from adult rats. Ex-vivo treatment with GHRH or CLON for 5 days was effective in stimulating GH biosynthesis only in the pituitary from neonatal rats. These data demonstrate that neonatal somatotropes are particularly sensitive to the GH-synthesizing activity of GHRH or a GHRH-releasing stimulus.

Accuracy of the urinary albumin titrator stick 'Micral-Test' in kidney-disease patients.

BACKGROUND: A quick, accurate, and easy measurement of microalbuminuria can be useful for the management of many patients. The Micral-Test stick (Boehringer Mannheim, Germany) gives a semiquantitative estimation of urinary albumin concentration at discrete readings of 0, 10, 20, 50 or 100 mg/l. The purpose of this study was to test its accuracy. METHODS: From 46 non-diabetic patients, 491 urinary samples were analysed both with Micral-Test and with immunochemical nephelometry. RESULTS: Of 491 samples, 308 were from non-proteinuric patients (urinary albumin < 300 mg/day). In these patients the correlation coefficient of nephelometric values versus the stick readings was 0.79: 120/123 samples from non-microalbuminuric (< or = 30 mg/24 h) and 164/185 from microalbuminuric patients were correctly identified by the stick, giving an 89% sensitivity and a 98% specificity. The readings around the threshold for microalbuminuria (20 and 50 mg/l patches) were the most reliable ones. Analysis of the correct/uncorrect readings' ratio for every patch in the 245 samples in the 0-150 mg/l range shows a relative uniformity (chi2 = 8.5, P = 0.07), while analysis of the over/correct/underreadings for the 10, 20 and 50 patches, shows that incorrect responses tend to be underestimations for the 10 patch and overestimations for the 20 and 50 mg/l patches (chi2 = 10.5, P = 0.03). CONCLUSIONS: The Micral-Test stick is useful for screening, but less reliable for follow-up, unless considerable changes in albumin excretion are expected.

Which urinary proteins are decreased after angiotensin converting--enzyme inhibition?

It is believed that angiotensin converting-enzyme (ACE) inhibitors lower proteinuria by acting on glomerular hemodynamics. This hypothesis predicts that the urinary excretion of a tubular protein should be unaffected by ACE inhibition. In the present study we have compared the excretion of albumin and Tamm-Horsfall Glycoprotein (THGP), a protein secreted only by renal tubules, before and after ACE inhibition. Urinary protein excretion was measured with the Phast System, a method based on SDS polyacrylamide gel electrophoresis followed by silver staining, in 15 essential hypertensives, after at least 4 weeks of wash-out from any drug and after 2 months of ACE inhibition with oral Quinapril. After 2 months of ACE inhibition, blood pressure (BP), body weight, urinary output, heart rate, plasma glucose, plasma and urinary creatinine, urate and electrolytes, and creatinine clearance, were not different from baseline values. Plasma ACE activity decreased from 76 +/- 7 to 10 +/- 4 U/mL (mean +/- SEM, 2 tails paired t test, p = 0.0001). Both albumin and THP urinary excretions decreased from 51 +/- 6 to 43 +/- 4 mg/ 24 h (p = 0.05) and from 19 +/- 3 to 12 +/- 1 mg/24 h (p = 0.02), respectively. This unexpected result suggests that ACE inhibitors may act also at the level of renal tubular cells.