RENAL EXCRETION OF ZINC IN NORMAL INDIVIDUALS DURING ZINC TOLERANCE-TEST AND GLUCOSE-TOLERANCE TEST

The urinary excretion, renal clearance, and tubular reabsorption of zinc were investigated in 30 adult healthy subjects under basal conditions and during the zinc and glucose tolerance tests. After a 12h overnight fast, each subject was submitted to renal clearance of zinc. The procedures were performed between 8.00 and 12.00 a.m., after emptying the bladder and ingestion of 4 ml deionized water/kg body weight at 8.00 a.m. The first urine sample was collected at 10.00 a.m., and the second at 12.00 a.m. A dose of 110 mg ZnSO4.7H(2)O was administered orally to each subject, diluted in 20 mi deionized water, at time 0 min. Blood samples were collected from an antecubital vein at times -30, 0, and 30 min and at 30 min intervals up to 240 min. Glucose was administered intravenously (0.5 ml 50%/kg body weight) during the first 3 min of the test, and blood samples were collected from an unconstricted, contralateral, antecubital vein at times -30, 0, 3, 5, 10, 20, 30, 45, 60, and 90 min. The results showed that urinary zinc excretion, and renal zinc clearance were significantly higher during the zinc and glucose tolerance tests than in the control condition. on the other hand, renal zinc clearance was more elevated during the glucose tolerance test than during the zinc tolerance test. Variations in zinc tubular reabsorption and glomerular filtration rate were not detected. The results suggest that urinary excretion and renal clearance of zinc in healthy subjects increase during acute zinc ingestion and glucose infusion. Although zinc ingestion raised urinary zinc excretion, glucose infusion was more effective in increasing renal zinc clearance. These normal parameters are important in the investigation of diabetic patients with serum and urine zinc changes.

Renal excretion of zinc in normal individuals during zinc tolerance test and glucose tolerance test

The urinary excretion, renal clearance, and tubular reabsorption of zinc were investigated in 30 adult healthy subjects under basal conditions and during the zinc and glucose tolerance tests. After a 12h overnight fast, each subject was submitted to renal clearance of zinc. The procedures were performed between 8.00 and 12.00 a.m., after emptying the bladder and ingestion of 4 ml deionized water/kg body weight at 8.00 a.m. The first urine sample was collected at 10.00 a.m., and the second at 12.00 a.m. A dose of 110 mg ZnSO47H2O was administered orally to each subject, diluted in 20 ml deionized water, at time 0 min. Blood samples were collected from an antecubital vein at times -30, 0, and 30 min and at 30 min intervals up to 240 min. Glucose was administered intravenously (0.5 ml 50%/kg body weight) during the first 3 min of the test, and blood samples were collected from an unconstricted, contralateral, antecubital vein at times -30, 0, 3, 5, 10, 20, 30, 45, 60, and 90 min. The results showed that urinary zinc excretion, and renal zinc clearance were significantly higher during the zinc and glucose tolerance tests than in the control condition. On the other hand, renal zinc clearance was more elevated during tile glucose tolerance test than during the zinc tolerance test. Variations in zinc tubular reabsorption and glomerular filtration rate were not detected. The results suggest that urinary excretion and renal clearance of zinc in healthy subjects increase during acute zinc ingestion and glucose infusion, Although zinc ingestion raised urinary zinc excretion, glucose infusion was more effective in increasing renal zinc clearance. These normal parameters are important in the investigation of diabetic patients with serum and urine zinc changes.

A genome-wide linkage scan for genes controlling variation in urinary albumin excretion in type ll diabetes

The main hallmark of diabetic nephropathy is elevation in urinary albumin excretion. We performed a genome-wide linkage scan in 63 extended families with multiple members with type II diabetes. Urinary albumin excretion, measured as the albumin-to-creatinine ratio (ACR), was determined in 426 diabetic and 431 nondiabetic relatives who were genotyped for 383 markers. The data were analyzed using variance components linkage analysis. Heritability (h2) of ACR was significant in diabetic (h2=0.23, P=0.0007), and nondiabetic (h2=0.39, P=0.0001) relatives. There was no significant difference in genetic variance of ACR between diabetic and nondiabetic relatives (P=0.16), and the genetic correlation (rG=0.64) for ACR between these two groups was not different from 1 (P=0.12). These results suggested that similar genes contribute to variation in ACR in diabetic and nondiabetic relatives. This hypothesis was supported further by the linkage results.

Genome-wide association study of urinary albumin excretion rate in patients with type 1 diabetes

Aims/hypothesis: An abnormal urinary albumin excretion rate (AER) is often the first clinically detectable manifestation of diabetic nephropathy. Our aim was to estimate the heritability and to detect genetic variation associated with elevated AER in patients with type 1 diabetes. 
 Methods: The discovery phase genome-wide association study (GWAS) included 1,925 patients with type 1 diabetes and with data on 24 h AER. AER was analysed as a continuous trait and the analysis was stratified by the use of antihypertensive medication. Signals with a p value <10^{−4 were followed up in 3,750 additional patients with type 1 diabetes from seven studies.} 
 Results: The narrow-sense heritability, captured with our genotyping platform, was estimated to explain 27.3% of the total AER variability, and 37.6% after adjustment for covariates. In the discovery stage, five single nucleotide polymorphisms in the GLRA3 gene were strongly associated with albuminuria (p < 5 × 10^{−8). In the replication group, a nominally significant association (p = 0.035) was observed between albuminuria and rs1564939 in GLRA3, but this was in the opposite direction. Sequencing of the surrounding genetic region in 48 Finnish and 48 UK individuals supported the possibility that population-specific rare variants contribute to the synthetic association observed at the common variants in GLRA3. The strongest replication (p = 0.026) was obtained for rs2410601 between the PSD3 and SH2D4A genes. Pathway analysis highlighted natural killer cell mediated immunity processes.} 
 Conclusions/interpretation: This study suggests novel pathways and molecular mechanisms for the pathogenesis of albuminuria in type 1 diabetes.

Splanchnic metabolism of nitrogenous compounds and urinary nitrogen excretion in steers fed alfalfa under conditions of increased absorption of ammonia and L-arginine supply across the portal-drained viscera

Effects of increased ammonia and/or arginine absorption across the portal-drained viscera (PDV) on net splanchnic (PDV and liver) metabolism of nitrogenous compounds and urinary N excretion were investigated in six cathetenzed Hereford x Angus steers (501 +/- 1 kg BW) fed a 75% alfalfa:25% (as-fed basis) corn-soybean meal diet (0.523 MJ of ME/[kg BW0.15.d]) every 2 h without (27.0 g of N/kg of dietary DM) and with 20 g of urea/kg of dietary DM (35.7 g of N/kg of dietary DM) in a split-plot design. Net splanchnic flux measurements were obtained immediately before beginning and ending a 72-h mesenteric vein infusion of L-arginine (15 mmol/h). For 3 d before and during arginine infusion, daily urine voided was measured and analyzed for N composition. Feeding urea increased PDV absorption (P < 0.01) and hepatic removal (P < 0.01) of ammonia N, accounting for 80% of increased hepatic urea N output (P < 0.01). Numerical increases in net hepatic removal of AA N could account for the remaining portion of increased hepatic urea N output. Arginine infusion increased hepatic arginine removal (P < 0.01) and hepatic urea N output (P < 0.03) and switched hepatic ornithine flux from net uptake to net output (P < 0.01), but numerical changes in net hepatic removal of ammonia and AA N could not account fully for the increase in hepatic urea N output. Increases in urine N excretion equaled quantities of N fed as urea or infused as arginine. Estimated salivary urea N excretion was not changed by either treatment. Urea cycle regulation occurs via a complex interaction of mechanisms and requires N sources other than ammonia, but the effect of increased ammonia absorption on hepatic catabolism of individual AA in the present study was not significant.

Participation of alpha-1 and alpha-2 adrenoceptors of the lateral hypothalamic area in water intake, and renal sodium, potassium and urinary Volume excretion induced by central administration of angiotensin II

The circumventricular structures and the lateral hypothalamus (LH) have been shown to be important for the central action of angiotensin II (ANGII) on water and electrolyte regulation. Several anatomical findings have demonstrated neural connection between circumventricular structures and the LH, the present experiments were conducted to investigate the role of the alpha-adrenergic antagonists and agonistic injected into the LH on the water intake, sodium and potassium excretion elicited by injections of ANGII into the lateral ventricle (LV), the water intake was measured every 30 min over a period of 120 min. The sodium, potassium and urinary volume were measured over a period of 120 min in water-loaded rats. The injection of ANGII into the LV increased the water intake, which was reduced by previous injection of clonidine (an alpha-2-adrenergic agonist) into the LH. The injection of yohimbine (an alpha-2-adrenergic antagonist) and prazosin (an alpha-l-adrenergic antagonist) into the LH, which was done before injecting ANGII into the LV, also reduced the water intake induced by ANGII. The injection of ANGII into the LV reduced the sodium, potassium and urinary volume. Previous treatment with clonidine attenuated the action of ANGII in reducing the sodium, potassium and urinary volume, whereas previous treatment with yohimbine attenuated the effects of ANGII but with less intensity than that caused by clonidine. Previous treatment with prazosin increased the inhibitory effects of ANGII in those parameters. The injection of yohimbine and prazosin, which was done before the injection of clonidine, attenuated the effect of clonidine on the ANGII mechanism. The results of this study led us to postulate that when alpha-2-adrenergic receptors are blocked, the clonidine may act on the imidazoline receptors to produce its effects on the ANGII mechanism. We may also conclude that the LH is involved with circumventricular structures, which present excitatory and inhibitory mechanisms. Such mechanisms are responsible for regulating the renal excretion of sodium, potassium and water, (C) 2000 Elsevier B.V.

THE ASSESSMENT OF ZINC STATUS BY THE ZINC TOLERANCE-TEST IN THYROID-DISEASE

Zinc status was evaluated in 12 hyperthyroid and in 7 hypothyroid patients in comparison with 8 euthyroid individuals by the oral zinc tolerance test and by the determination of urinary zinc excretion. Hyperthyroid patients presented a basal serum concentration similar to that of euthyroid individuals but greater urinary zinc excretion, indicating the occurrence of zinc depletion from tissues to the blood stream caused by the catabolism inherent in the hyperthyroid state. Hyperthyroidism also caused lower zinc assimilation by tissues after zinc ingestion. Hypothyroid individuals present lower basal zinc levels in serum than euthyroid and hyperthyroid individuals and urinary zinc excretion similar to that of euthyroid individuals. No changes in the parameters measured were observed after zinc load, suggesting reduced or delayed intestinal absorption and zinc assimilation by tissues. The present data are indicative of zinc deficiency, the lower intestinal zinc absorption probably being one of the contributing factors.

Maxi-K channels contribute to urinary potassium excretion in the ROMK-deficient mouse model of Type II Bartter's syndrome and in adaptation to a high-K diet

Type II Bartter's syndrome is a hereditary hypokalemic renal salt-wasting disorder caused by mutations in the ROMK channel (Kir1.1; Kcnj1), mediating potassium recycling in the thick ascending limb of Henle's loop (TAL) and potassium secretion in the distal tubule and cortical collecting duct (CCT). Newborns with Type II Bartter are transiently hyperkalemic, consistent with loss of ROMK channel function in potassium secretion in distal convoluted tubule and CCT. Yet, these infants rapidly develop persistent hypokalemia owing to increased renal potassium excretion mediated by unknown mechanisms. Here, we used free-flow micropuncture and stationary microperfusion of the late distal tubule to explore the mechanism of renal potassium wasting in the Romk-deficient, Type II Bartter's mouse. We show that potassium absorption in the loop of Henle is reduced in Romk-deficient mice and can account for a significant fraction of renal potassium loss. In addition, we show that iberiotoxin (IBTX)-sensitive, flow-stimulated maxi-K channels account for sustained potassium secretion in the late distal tubule, despite loss of ROMK function. IBTX-sensitive potassium secretion is also increased in high-potassium-adapted wild-type mice. Thus, renal potassium wasting in Type II Bartter is due to both reduced reabsorption in the TAL and K secretion by max-K channels in the late distal tubule. © 2006 International Society of Nephrology.

Urinary fluoride excretion in children exposed to fluoride toothpaste and to different water fluoride levels in a tropical area of Brazil

The aim of this study was to evaluate the urinary fluoride excretion of 2- to 7-year-old children exposed to different water fluoride concentrations in the city of Catolé do Rocha, PB, Brazil. Forty-two children were allocated to 3 groups according to the concentration of fluoride in the water: G1 (n=10; 0.5-1.0 ppm F), G2 (n=17; 1.1-1.5 ppm F) and G3 (n= 15; >1.51 ppm F). The study was carried out in two 1-week phases with 1-month interval between the moments of data collection: in the first phase, the children used a fluoride toothpaste (FT) (1,510 ppm F) for 1 week, whereas in the second phase a non-fluoride toothpaste (NFT) was used. The urine was collected in a 24-h period in each week-phase according to Marthaler's protocol. The urinary fluoride excretion data expressed as mean (SD) in ì g/24 h were: G1-FT= 452.9 (290.2); G1-NFT= 435.1 (187.0); G2-FT= 451.4 (224.0); G2-NFT= 430.3 (352.5); G3-FT=592.3 (390.5); and G3-NFT=623.6 (408.7). There was no statistically significant difference between the water fluoride groups, and regardless of the week phase (ANOVA, p>0.05). The use of fluoride toothpaste (1,510 ppmF) did not promote an increase in urinary fluoride excretion. There was a trend, though not significant, as to the increase of urine fluoride concentration in relation to fluoride concentrations in the water. The excretion values suggest that some children are under risk to develop dental fluorosis and information about the appropriate use of fluoride is necessary in this area.

Mucopolysaccharidoses in northern Brazil: targeted mutation screening and urinary glycosaminoglycan excretion in patients undergoing enzyme replacement therapy

Mucopolysaccharidoses (MPS) are rare lysosomal disorders caused by the deficiency of specific lysosomal enzymes responsible for glycosaminoglycan (GAG) degradation. Enzyme Replacement Therapy (ERT) has been shown to reduce accumulation and urinary excretion of GAG, and to improve some of the patients' clinical signs. We studied biochemical and molecular characteristics of nine MPS patients (two MPS I, four MPS II and three MPS VI) undergoing ERT in northern Brazil. The responsiveness of ERT was evaluated through urinary GAG excretion measurements. Patients were screened for eight common MPS mutations, using PCR, restriction enzyme tests and direct sequencing. Two MPS I patients had the previously reported mutation p.P533R. In the MPS II patients, mutation analysis identified the mutation p.R468W, and in the MPS VI patients, polymorphisms p.V358M and p.V376M were also found. After 48 weeks of ERT, biochemical analysis showed a significantly decreased total urinary GAG excretion in patients with MPS I (p < 0.01) and MPS VI (p < 0.01). Our findings demonstrate the effect of ERT on urinary GAG excretion and suggest the adoption of a screening strategy for genotyping MPS patients living far from the main reference centers.

Undernutrition fetal programming: effects on kidney morphology, renal steroid and angiotensin receptors expression and urinary sodium excretion

Maternal undernutrition affects the foetal development, promoting renal alterations and adult hypertension. The present study investigates, in adult male rats, the effect of food restriction in utero on arterial blood pressure changes (AP), and its possible association with the number of nephrons, renal function and angiotensin II (AT1R/AT2R), glucocorticoid (GR) and mineralocorticoid (MCR) receptors expression. The daily food supply to pregnant rats was measured and one group (n=5) received normal quantity of food (NF) while the other group received 50% of that (FR50) (n=5). The AP was measured weekly. At 16 weeks of life, fractionator’s method was used to estimate glomeruli number in histological slices. The renal function was estimate by creatinine and lithium clearances. Blood and urine samples were collected to biochemical determination of creatinine, sodium, potassium and lithium. At 90th and 23rd days of life, kidneys were also processed to AT1R, AT2R, GR and MCR immunolocalization and for western blotting analysis. FR50 offspring shows a significant reduction in BW (FR50: 5.67 ± 0.16 vs. 6.84 ± 0.13g in NF, P<0.001) and increased AP from 6th to 12nd week (6thwk FR50: 149.1 ± 3.4 vs. 125.1 ± 3.2mmHg in NF, P<0.001and, 12ndwk FR50: 164.4 ± 4.9 vs. 144.0 ± 3.3 mmHg in NF, P=0.02). Expression of AT1R and AT2R were significantly decreased in FR50 (AT1, 59080 ± 2709 vs. 77000 ± 3591 in NF, P=0.05; AT2, 27500 ± 95.50 vs. 67870 ± 1509 in NF, P=0.001) while the expression of GR increased in FR50 (36090 ± 781.5 vs. 4446 ± 364.5 in NF, P=0.0007). The expression of MCR did not change significantly. We also verified a pronounced decrease in fractional urinary sodium excretion in FR50 offspring (0.03 ± 0.02 vs. 0.06 ± 0.04 in NF, p=0.03). This occurred despite unchanged creatinine clearance. The study led us to suggest that fetal undernutrition, with increased fetal exposure... (Complete abstract click electronic access below)

Fetal kidney programming by severe food restriction: effects on structure, hormonal receptor expression and urinary sodium excretion in rats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)