Adrenal enzyme impairment in neonates and adolescents treated with ritonavir and protease inhibitors for HIV exposure or infection.

BACKGROUND: Human deficiency virus (HIV) protease inhibitors (PIs) are widely used drugs whose effects are pharmacologically enhanced by ritonavir, a potent cytochrome P450 inhibitor. We reported previously that prophylactic postnatal ritonavir-PI therapy in HIV-exposed neonates was associated with increases in plasma 17-hydroxyprogesterone (17-OHP) and dehydroepiandrosterone sulfate (DHEA-S). AIMS: To further investigate adrenal function in neonates and adolescents given ritonavir-PI. METHODS: Adrenal function was assessed prospectively in 3 HIV-exposed neonates given short-term prophylactic treatment and 3 HIV-infected adolescents given long-term treatment. Plasma cortisol, 17-OHP, 17-OH-pregnenolone, DHEA-S, and androstenedione were measured before and after ACTH administration. RESULTS: None of the patients had clinical signs of adrenal dysfunction. The only neonate exposed to ritonavir-PI in utero had up to 3-fold increases in plasma 17-OHP. Increases in 17-OH-pregnenolone of up to 3.1-fold were noted in 4 of the 6 patients, and all 6 patients had elevations in DHEA-S (up to 20.4-fold increase) and/or DHEA (up to 4.7-fold) and/or androstenedione (up to 5.2-fold). All these parameters improved after treatment completion. CONCLUSION: Neonates and adolescents given ritonavir-PI exhibit a similar adrenal dysfunction profile consistent with an impact on multiple adrenal enzymes. These abnormalities require evaluation, given the potentially long exposure times.

Childhood craniopharyngioma: hypothalamus-sparing surgery decreases the risk of obesity.

CONTEXT: Craniopharyngioma is a brain tumor whose high local recurrence rate has for a long time led to a preference for extensive surgery. Limited surgery minimizing hypothalamic damage may decrease the severe obesity rate at the expense of the need for radiotherapy to complete the treatment. OBJECTIVE: We compared weight gain and local recurrence rates after extensive resection surgery (ERS) and hypothalamus-sparing surgery (HSS). DESIGN: Our observational study compared a historical cohort managed with ERS between 1985 and 2002 to a prospective cohort managed with HSS between 2002 and 2010. SETTING: The patients were treated in a pediatric teaching hospital in Paris, France. PATIENTS: Thirty-seven boys and 23 girls were managed with ERS (median age, 8 years); 38 boys and 27 girls were managed with HSS (median age, 9.3 years). MAIN OUTCOME MEASURES: Data were collected before and 6 months to 7 years after surgery. Body mass index (BMI) Z-score was used to assess obesity and the number of surgical procedures to assess local recurrence rate. RESULTS: Mean BMI Z-score before surgery was comparable in the 2 cohorts (0.756 after ERS vs 0.747 after HSS; P = .528). At any time after surgery, mean BMI Z-score was significantly lower after HSS (eg, 1.889 SD vs 2.915 SD, P = .004 at 1 year). At last follow-up, the HSS cohort had a significantly lower prevalence of severe obesity (28% vs 54%, P < .05) and higher prevalence of normal BMI (38% vs 17%, P < .01). Mean number of surgical procedures was not significantly different in the 2 cohorts. CONCLUSIONS: Hypothalamus-sparing surgery decreases the occurrence of severe obesity without increasing the local recurrence rate.

Effects on growth and metabolism of growth hormone treatment for 3 years in 36 children with Prader-Willi syndrome.

BACKGROUND/AIMS: Prader-Willi syndrome (PWS) is a complex genetic disorder whose many manifestations include obesity and short stature. Diabetes, osteoporosis, and scoliosis are common. We evaluated the effects of human growth hormone (hGH). METHODS: A prospective cohort study of 36 children (1-15 years of age) with genetically confirmed PWS who were given hGH (mean dose 0.033 ± 0.006 mg/kg/day) for 36 months. At baseline and once yearly, we evaluated growth, insulin-like growth factor-1 (IGF-1), body composition, bone mineral density (BMD), glucose tolerance, serum lipids, and spinal radiographs. RESULTS: Height gain over the 3-year period was 1.2 SD score. Lean body mass increased significantly during each treatment year. Total body fat decreased by 5.42 and 1.17% in the 1st and 2nd years, respectively. BMD remained unchanged during therapy. IGF-1 and homeostasis model assessment index of insulin resistance increased, and glucose intolerance was found in 22.7% of patients at baseline and 0% at 3 years. None of the patients had diabetes. Their lipid profile improved. Scoliosis was present in 27.8% of the patients at baseline and 47.2% at 3 years. CONCLUSION: GH treatment in children with PWS has multiple beneficial effects on growth and body composition. Tolerance is good, with an improvement in glucose metabolism, although IGF-1 levels and insulin resistance parameters should be monitored closely. The high rate of scoliosis warrants monitoring by a pediatric orthopedic surgeon.

Evaluation of the effect of autologous mesenchymal stem cell injection in a large-animal model of bilateral kidney ischaemia reperfusion injury.

OBJECTIVES: Adult mesenchymal stem cells (MSC) have been proven to be of benefit to the kidney in different experimental models of renal injuries. All studies have been performed in valuable rodent models, but the relevance of these results to large mammals and ultimately, to humans remains unknown. Therefore, the aim of this study was to investigate the effect of MSC transplantation in an alternative ovine large-animal model of bilateral kidney ischaemia reperfusion injury. MATERIAL AND METHODS: Sheep were divided into three groups: one sham-operated group and two groups submitted to renal bilateral ischaemia for 60 min. Animals with ischaemia reperfusion injury were treated with injection of autologous MSCs or with vehicle medium. RESULTS: The model sheep presented with renal histological manefestations that closely resembled lesions seen in patients. Transplanted MSCs were found in glomeruli but not in tubules and did not express glomerular cell markers (podocin, von Willebrand factor), but functional evaluation showed no beneficial effect of MSC infusion. Morphological and molecular analyses corroborated the functional results. MSCs did not repair kidney parenchyma and failed to modulate cell death and proliferation or cytokine release (tumour necrosis factor-alpha, vascular endothelial growth factor alpha (VEGF-alpha), Bcl-2, caspase). CONCLUSION: In this unique autologous large-animal model, MSCs did not exhibit reparative or paracrine protective properties.

Sirolimus may reduce fertility in male renal transplant recipients.

Assessment of sex hormones in organ transplant recipients suggests that sirolimus may impair testicular function. The aim of this study was to evaluate the frequency and severity of sirolimus-associated alterations in sperm parameters and their impact on fathered pregnancy rate. An observational study was carried out in male patients aged 20-40 years who received a kidney transplant during 1995-2005. Patients were sent a questionnaire by post, and sperm analysis was proposed. The fathered pregnancy rates according to the immunosuppressive regimen were estimated and compared using the Poisson model. Complete information was obtained from 95 out of 116 recipients. Patients treated with sirolimus throughout the post-transplant period had a significantly reduced total sperm count compared to patients who did not receive sirolimus (28.6 +/- 31.2 x 10(6) and 292.2 +/- 271.2 x 10(6), respectively; p = 0.006), and a decreased proportion of motile spermatozoa (22.2 +/- 12.3% and 41.0 +/- 14.5%, p = 0.01). Moreover, the fathered pregnancy rate (pregnancies/1000 patient years) was 5.9 (95% CI, 0.8-42.1) and 92.9 (95% CI, 66.4-130.0) in patients receiving sirolimus-based and sirolimus-free regimens, respectively (p = 0.007). Of six patients in whom sirolimus treatment was interrupted, only three showed a significant improvement in sperm parameters. Sirolimus is associated with impaired spermatogenesis and, as a corollary, may reduce male fertility.

Luteinizing hormone pulsatility in patients with major ovarian hyperandrogenism.

Hyperandrogenism and ovulatory dysfunction are common in women with either polycystic ovary (PCOS) or ovarian virilizing tumor. However, contrasting with the numerous studies that have extensively described gonadotropin secretory abnormalities, principally increased LH pulse amplitude and frequency, few studies have concerned gonadotropin secretion in patients with ovarian virilizing tumors; low gonadotropin levels have occasionally been reported, but never extensively studied. The goal of the present study was to further evaluate the pulsatility of LH secretion in women with ovarian virilizing tumor compared with that of PCOS patients. Eighteen women with major hyperandrogenism (plasma testosterone level >1.2 ng/ml) were studied (5 women with ovarian virilizing tumor, 13 women with PCOS, and 10 control women). Mean plasma LH level, LH pulse number and amplitude were dramatically low in patients with ovarian tumors when compared to both PCOS (p<0.001) and controls (p<0.001). In case of major hyperandrogenism, LH pulse pattern differs markedly between women with ovarian virilizing tumor or PCOS, suggesting different mechanisms of hypothalamic or pituitary feedback.

Breast inflammatory gigantomastia in a context of immune-mediated diseases.

CONTEXT: Localized breast lesions have been described in lupic or diabetic patients. However, the description of breast gigantomastia in women presenting with autoimmune diseases has not been reported. SETTING: The study took place within the Department of Endocrinology and Reproductive Medicine, Necker Hospital, Paris, France. PATIENTS: We describe eight patients with inflammatory gigantomastia, occurring in a context of immune-mediated diseases: myasthenia, chronic arthritis, or thyroiditis. MAIN OUTCOME MEASURES: Together with hormonal, immunological, and breast magnetic resonance imaging (MRI) evaluation, breast histology enabled us to perform immunocytochemical and indirect immunofluorescence studies. Control sera were obtained from patients with (n = 10) and without (n = 7) antinuclear antibodies. RESULTS: Six of the eight patients developed gigantomastia either at puberty or during pregnancy. Neither a hormonal oversecretion nor a specific immunological pattern was observed. All patients except one presented antinuclear antibodies. Histological study revealed a diffuse, stromal hyperplasia and a severe atrophy of the lobules. A rarefaction of adipocytes was also noted, as previously suggested on MRI. There was a perilobular lymphocytic infiltrate made of CD3+ lymphocytes. Study of sera from five of six cases of gigantomastia showed a nuclear immunofluorescence pattern in normal mammary ductal and lobular glandular epithelium, as well as in kidney and intestine epithelial cells. In control sera, a nuclear signal was observed only when antinuclear antibodies were present. CONCLUSIONS: We suggest that breast tissue may be a target tissue in autoimmune diseases, this process being favored by the hormonal milieu. However, the precise mechanism of such association is not individualized. The fact that stromal hyperplasia is the main histological feature justifies the search for the involvement of growth factors in such a process.

Significance of ovarian histology in the management of patients presenting a premature ovarian failure.

BACKGROUND: Premature ovarian failure (POF) is a heterogeneous syndrome, possibly due to mutations of genes involved in the normal development of the ovary and/or follicles. Based essentially on animal models, these mutations are associated with various ovarian phenotypes, from a complete absence of follicles to a partial follicular maturation. The aim of the present study was to determine whether ovarian histology, compared to pelvic ultrasonography, would be helpful in identifying which patients display an impaired follicular reserve and/or growth, and in orientating the search for POF aetiology. METHODS AND RESULTS: We studied a cohort of 61 patients suffering from POF with a normal karyotype. Their median age (range) at diagnosis was 26 years (15-39). The FSH plasma level was high, 67.0 IU/l (13-155). Estradiol and inhibin B plasma levels were low: 18.5 pmol/l (18.5-555) and 5 pg/ml (5-105) respectively. Both pelvic ultrasonography and ovarian biopsies were performed in each patient. The presence of follicles suggested at ultrasonography was confirmed at histology in 56% of the patients. Ovarian histology led to the distinction of two phenotypes: (i) small-sized ovaries, deprived of follicles; and (ii) normal-sized ovaries with partial follicular maturation. To confirm the value of ovarian biopsies, samples from 20 normal women were studied. These demonstrated that ovarian biopsy at random enables reliable assessment of follicular presence, especially when their size is <2 mm. CONCLUSION: Ovarian histology appears to be a reliable tool in evaluating the follicular reserve, and helpful and complementary to clinical and hormonal phenotyping in orienting the search for the various genetic causes of POF syndrome.

Pancreatic arterial calcium stimulation in the diagnosis and localisation of persistent hyperinsulinemic hypoglycaemia of infancy.

BACKGROUND: Persistent hyperinsulinemic hypoglycaemia of infancy (PHHI) is often resistant to medical therapy. Surgery is therefore necessary. It is due to focal adenomatous islet-cell hyperplasia treatable by partial pancreatectomy, or diffuse beta-cell hyperfunction, which requires near-total pancreatectomy. Pancreatic venous sampling (PVS) is the reference technique for the preoperative diagnosis and localization of focal forms of PHHI in the pancreas. However, hypoglycaemia is necessary to analyse the results and PVS is technically challenging. Pancreatic arterial calcium stimulation (PACS) is technically easier and does not require hypoglycaemia. AIM: To study the accuracy in the diagnosis and localization of PHHI. MATERIALS AND METHODS: PACS was performed in 12 patients and correlated with histology. RESULTS: The accuracy of PACS is poor in diffuse lesions since only two of six cases were correctly identified by this test. Five of six focal lesions were correctly recognized and located. CONCLUSIONS: PACS is less accurate than PVS in PHHI. Currently, it should be performed only when PVS fails.

Recovery after relief of fetal urinary obstruction: morphological, functional and molecular aspects.

The effects of obstruction [urinary tract obstruction (UTO)] and relief on renal development were examined in an experimental model in the fetal lamb. Bladder outlet obstruction was performed at 60 days of gestation; relief was performed by vesicoamniotic shunting at 90 days of gestation. Studies were carried out in obstructed (OF60; n = 11), shunted (SF; n = 5), and control fetuses (CF; n = 11) at 120 days of gestation. Fetal UTO produced either hydronephrosis (64%) or dysplasia (36%); dysplasia was always associated with a reduction in the number of glomeruli [950 +/- 99 (dysplasia) vs. 1,852 +/- 249 (CF) glomeruli/section]. Obstructed fetuses had lower creatinine clearance [0.76 +/- 0.41 (OF60) vs. 0.96 +/- 0.21 (CF) ml x min(-1) x kg(-1)], higher sodium fractional excretion [17.2 +/- 20.3 (OF60) vs. 2.4 +/- 3.7% (CF)], and higher urinary concentration [80 +/- 30 (OF60) vs. 43 +/- 22 (CF) micromol/l] than controls. In SF, the number of glomeruli was increased at 120 days of gestation (1,643 +/- 106 glomeruli/section) compared with nondiverted fetuses (1,379 +/- 502 glomeruli/section), and the temporal pattern of PAX2, disrupted after obstruction, was restored. In conclusion, early fetal UTO leads to either renal hydronephrosis with normal glomerular development or dysplasia with a decreased number of glomeruli; in utero urine diversion performed before the end of nephrogenesis may allow a reversal of the glomerulogenesis arrest observed.

Nephrogenesis and angiotensin II receptor subtypes gene expression in the fetal lamb.

To investigate the role of angiotensin II (ANG II) in nephrogenesis, a developmental study of renal AT1 and AT2 receptor mRNA expression was performed in parallel with the quantitative and qualitative analysis of metanephros development in fetal lamb from 60 to 140 days of gestation. Both ANG II receptor subtypes were expressed early during nephrogenesis but displayed specific spatial and temporal distribution during gestation. High-AT2 mRNA expression took place in the outermost nephrogenic area and in the undifferentiated mesenchymal cells surrounding the ampulla; level of AT2 expression in this localization followed closely glomeruli proliferation rate and disappeared after nephrogenesis completion (>120 days). AT2 mRNA was also detected in the differentiated epithelial cells of macula densa of maturing glomeruli. Although most of AT1 mRNA labeling was found in the mesangial cells of maturing glomeruli, where it persisted after nephrogenesis completion, additional labeling was found in undifferentiated cells, in cells invading the inferior cleft of S-shaped bodies (80 days), and in medullar cells between tubules (120 days). Our results suggest that each receptor subtype has a specific role in renal morphogenesis, i.e., AT2 in mesenchymal proliferation or apoptosis and AT1 in vascular smooth muscle cells differentiation.

Familial hyperproinsulinaemia due to a mutation substituting histidine for arginine at position 65 in proinsulin: identification of the mutation by restriction enzyme mapping.

UNLABELLED: Familial hyperproinsulinaemia is a rare genetic disorder characterized by point mutations in the insulin gene which impair the conversion of proinsulin to insulin. We report here three members of a two-generation Caucasian family in whom this syndrome was identified by unexplained hyperinsulinism associated with normal glucose tolerance and normal insulin sensitivity. Plasma insulin immunoreactivity showed a reduced affinity for the insulin receptor and eluted mainly, on Biogel chromatography, at the position of proinsulin. Analysis of the PCR-amplified insulin gene by restriction enzyme mapping revealed a new recognition site for the enzyme Nla III, indicating a Arg65 to His mutation. Sequence analysis of exon 3 confirmed this mutation in one allele of the gene. CONCLUSION: This study reports a two-generation European-Caucasian family with hyperproinsulinaemia due to a substitution of His for Arg at position 65 in proinsulin, the seventh now identified worldwide and the second from Europe. The mutation generated a new restriction site on the insulin gene suggesting the usefulness of restriction enzyme mapping as a screening procedure.

Experimental bilateral urinary obstruction in fetal sheep: transforming growth factor-beta 1 expression.

To gain insight into the role of transforming growth factor-beta 1 (TGF-beta 1) in the development of kidney pathology following fetal obstruction, we measured TGF-beta 1 gene expression, the active peptide, and the urinary concentration in a model of fetal bilateral urinary obstruction (BUO) in sheep. Fetal lambs underwent BUO at 60 (FO-60) or 80 days (FO-80) of gestation and were studied at 120 days. Independently of the onset or duration of obstruction, all fetuses developed type IV dysplasia (IV) associated with an arrest in the nephrogenesis or hydronephrosis. Fetal glomerular filtration rate was not significantly modified, whereas sodium tubular reabsorption was significantly decreased, and urinary TGF-beta 1 concentration was elevated in hydronephrosis but not in IV. Levels of TGF-beta 1 mRNA were increased in hydronephrosis compared with normal kidneys, and active TGF-beta 1 immunoreactivity was increased in both hydronephrotic and IV kidneys. In summary, TGF-beta 1 may play a role in the development of hydronephrosis and dysplasia in kidneys following fetal BUO. Its role in the arrest of nephrogenesis observed in the IV kidneys remains to be proved.

Insulin responses to intravenous glucose, intravenous arginine and a hyperglycaemic clamp in ICA-positive subjects with different degrees of glucose tolerance.

The relationship between altered insulin secretion and impaired glucose tolerance was studied in 32 non-obese subjects aged 14-49 years with islet-cell antibodies (ICA) and fasting blood glucose below 7.9 mmol/l, using oral (OGTT) and intravenous (IVGTT) glucose tolerance tests. Glucose tolerance was normal in 19 subjects, impaired (IGT) in 4 and satisfied diabetic criteria in 9. Fifteen of these subjects and 8 ICA-negative controls also underwent a hyperglycaemic clamp (10 mmol/l) and a glucose-potentiated IV arginine bolus. Acute insulin response to IVGTT and insulin and C-peptide responses to the hyperglycaemic clamp and the arginine bolus were dramatically lower (p < 0.001) in diabetic and IGT subjects than in ICA-positive patients with normal glucose tolerance and control subjects. Insulin responses to the three tests were inversely correlated with plasma glucose levels and the area under the curve of OGTT. The correlations between the degree of glucose tolerance and insulin responses to IVGTT, the hyperglycaemic clamp and the arginine bolus were virtually identical. It is concluded that insulin responses to the three stimuli were severely altered in ICA-positive patients with impaired glucose tolerance or asymptomatic diabetes, normal in normotolerant ICA-positive subjects, and correlated with glucose tolerance.

Cyclosporin A does not delay insulin dependency in asymptomatic IDDM patients.

OBJECTIVE: To measure the effects of cyclosporin A (CyA) with no insulin therapy on glucose tolerance and beta-cell function in the preclinical phase of insulin-dependent diabetes mellitus (IDDM). RESEARCH DESIGN AND METHODS: beta-cell responses to the intravenous glucose tolerance test (IVGTT), hyperglycemic clamp, intravenous arginine, and intravenous glucagon were evaluated before and after a 6-month course of CyA in seven patients (mean age 19.6 years) with asymptomatic IDDM. RESULTS: Initial insulin secretory responses were severely decreased when the patients were compared with eight healthy control subjects: IVGTT (1 + 3 min): 106 +/- 16 vs. 884 +/- 190 pmol/l (P < 0.001); hyperglycemic clamp: 102 +/- 16 vs. 310 +/- 42 pmol/l (P < 0.001); intravenous arginine: 346 +/- 72 vs. 1104 +/- 168 pmol/l (P < 0.01); and intravenous glucagon: 170 +/- 37 vs. 247 +/- 35 pmol/l (NS). The beta-cell responses remained markedly abnormal after 6 months of CyA, although the response to intravenous glucose and oral glucose tolerance tests improved in three subjects. All the patients became insulin-dependent after 5-36 months. CONCLUSIONS: CyA alone is not a suitable treatment for asymptomatic IDDM. Earlier identification of subjects with substantial beta-cell secretory capacity and newer nontoxic intervention strategies are required for the prevention of IDDM.

Fetal urinary insulin-like growth factor I and binding protein 3 in bilateral obstructive uropathies.

Fetal urinary concentrations of insulin-like growth factor I (UIGF-I) and binding protein 3 (UIGFBP-3) were determined in patients with prenatal diagnosis of bilateral obstructive uropathy. Patients were retrospectively assigned to three groups, on the basis of outcome: group 1, termination of pregnancies (n = 11) with sonographic evidence of severe oligohydramnios or renal dysplasia, confirmed at histological examination; group 2, patients (n = 10) with postnatal plasma creatinine > 50 mumol/l at the age of 1 year (1 yr-pCreat); and group 3, patients (n = 16) with 1 yr-pCreat < or = mumol/l. The results show a significant increase in UIGF-I and UIGFBP-3 in groups 1 (18,159 +/- 9083 pg/ml; 2657 +/- 669 ng/ml) and 2 (1574 +/- 847 pg/ml; 176 +/- 50 ng/ml) in comparison with group 3 (35 +/- 6 pg/ml; 21 +/- 2 ng/ml). UIGF-I and UIGFBP-3 were significantly correlated with postnatal plasma creatinine, and were both sensitive (90 per cent; 80 per cent) and specific (88 per cent; 88 per cent) for prediction of elevated 1 yr-pCreat (> 50 mumol/l). Fetal urinary IGF-I and IGFBP-3 are increased in severe fetal bilateral obstructive uropathy, possibly reflecting tubular dysfunction or/and increased synthesis consequent upon fetal kidney injury. Their predictive value for postnatal renal function needs further assessment.

Influence of glucagon on GFR and on urea and electrolyte excretion: direct and indirect effects.

Clearance experiments were performed in anesthetized male Wistar rats to determine the level of peripheral glucagon concentration required to elicit changes in glomerular filtration rate (GFR) and in solute excretion. Glucagon was intravenously infused at a rate of 1.25 (group G-1, n = 8), 3.75 (group G-3, n = 7), or 12.5 (group G-10, n = 7) ng.min-1.100 g body wt-1 for 100 min. Measurements were performed before, during, and after this infusion. Group G-10 resulted in a plasma concentration of glucagon severalfold higher than usually observed in peripheral blood after a protein meal but normal for the hepatic circulation. Group G-10 simultaneously increased GFR, plasma adenosine 3',5'-cyclic monophosphate (cAMP) concentration, and the excretion of water (i.e., urinary flow rate), Na, Cl, PO4, K, and urea. Some of the effects of glucagon on electrolyte excretion were also observed with group G-1 and/or G-3 and were fully reversible, suggesting a direct renal action of glucagon. The significant and reversible increase in K excretion in group G-3 suggests that glucagon exerts a direct stimulatory influence on K secretion in the distal nephron. Increases in urinary flow rate, PO4, Na, and urea fractional excretions were seen with group G-10 only and were not reversible, suggesting an indirect action of glucagon on the proximal tubule. Because glucagon stimulates cAMP formation in hepatocytes and because this cAMP is released in the blood and secreted by proximal tubule cells, cAMP of hepatic origin could induce a parathyroid hormone-like effect in this nephron segment. In summary, these experiments suggest that glucagon influences different aspects of renal function by a combination of direct and indirect (probably liver-dependent) effects.

Mechanisms of dopamine effects on Na-K-ATPase activity in Madin-Darby canine kidney (MDCK) epithelial cells.

Dopamine decreases tubular sodium reabsorption, attributed in part to Na-K-ATPase inhibition in the proximal convoluted tubule (PCT). Because the final regulation of sodium excretion occurs in the collecting duct, where specific dopamine DA1 binding sites have been demonstrated, we examined the effects of dopamine, as well as of DA1 and DA2 receptor agonists on Na-K-ATPase activity and on the number of units in Madin-Darby canine kidney (MDCK) cells, which retain differentiated properties of the renal cortical collecting tubule epithelium. Dopamine (10(-5) M) inhibited pump activity (by 50%) and reduced the number of units. This effect was reproduced by the DA1 agonist SKF 38393, which inhibited pump activity in a dose- and time-dependent manner (maximum, 10(-5) M). The DA2 agonist quinpirole hydrochloride was without effect, either alone or in combination with SKF 38393. Inhibition of pump activity by dopamine was totally abolished by H7 (100 microM), an inhibitor of protein kinase (PK), but partially by 2',5'-dideoxy-adenosine (DDA) and H4, respective inhibitors of cAMP production and PKA, which suggests that the dopamine effect on Na-K-ATPase activity may be linked to activation of both PKC and PKA. In these cells, amiloride addition during preincubation did not alter the effect of dopamine on Na-K-ATPase activity; in contrast, furosemide increased further the inhibitory effect of dopamine on the enzyme activity. Monensin addition (10(-3) M) reversed the inhibitory effect of dopamine after a 30-min preincubation.(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin responses to intravenous glucose and the hyperglycemic clamp in cystic fibrosis patients with different degrees of glucose tolerance.

The relationship between altered insulin secretion and impaired glucose tolerance was studied in 32 cystic fibrosis patients, 16 men and 16 women, aged 8-26 y, using oral and i.v. glucose tolerance tests and a hyperglycemic glucose clamp (10 mmol/L). Seven of these subjects were already being treated with insulin; seven had fasting blood glucose levels below 7.2 mmol/L but satisfied diabetic criteria at the oral glucose tolerance test; glucose tolerance was impaired in 13 subjects and normal in five. The insulin responses to the two i.v. glucose stimuli were inversely correlated with the plasma glucose levels (60 and 120 min) and the area under the curve of the oral glucose tolerance test. However, the acute insulin response to i.v. glucose was severely altered in patients with impaired glucose tolerance, whereas plasma insulin levels during the hyperglycemic clamp did not differ from those of healthy subjects. The responses to the two stimuli were dramatically low in the diabetic patients. These results suggest that cystic fibrosis patients with normal or impaired glucose tolerance retain their capacity to secrete insulin. Alterations in the acute phase of glucose-stimulated insulin secretion seem to be principally responsible for the early impairment in glucose tolerance.

Acute renal effects of neutral endopeptidase inhibition in humans.

The acute renal effects of neutral endopeptidase 24.11 (E-24.11) inhibition induced by a single oral dose of sinorphan (100 mg) were investigated in 10 healthy normotensive subjects on normal sodium diet. Sinorphan inhibited 90% of E-24.11 activity and increased plasma atrial natriuretic peptide (ANP) and urinary guanosine 3',5'-cyclic monophosphate (cGMP) by 70 and 100%, respectively. Sinorphan increased urinary sodium output by 50% (P < 0.001) and decreased fractional distal reabsorption by 4% (P < 0.01). Sinorphan increased glomerular filtration rate (GFR) and filtration fraction by 10% 1 h after administration and decreased renal plasma flow by 10%. Mean arterial pressure, renal vascular resistance, plasma aldosterone concentration, and renin activity were unmodified. Sinorphan decreased fractional clearance of neutral dextrans over the 34- to 52-A radius range. Applying the changes along with a hydrodynamic isopore with shunt model, sinorphan significantly increased capillary pressure gradient (delta P; 39 +/- 1 vs. 34 +/- 1 mmHg; P < 0.01), whereas ultrafiltration coefficient was unchanged. In conclusion, endopeptidase inhibition increased endogenous plasma ANP and cGMP generation and induced natriuresis through both an increase in filtered load and a decrease in distal tubular reabsorption of sodium. Sinorphan increases GFR, filtration fraction, and delta P, probably through an increase in efferent over afferent arteriolar resistance ratio.