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Query: UNIPROT:P41181 (collecting duct)
 5,183 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

During the past 5 years, we have identified idiopathic hypercalciuria in five of seven patients referred for evaluation of renal glycosuria between 1985 and 1991. The children, all boys, ranged in age from 6 to 12 years. Endocrine function was normal, and none of the patients had hyperparathyroidism, hypercalcemia, renal tubular acidosis, or other secondary causes of hypercalciuria. The calcium/creatinine ratio in a fasting urine specimen was elevated in all five children who had hypercalciuria, with a mean value (+/- SD) of 0.34 +/- 0.06 (normal, < 0.2). In one child who had renal colic with spontaneous passage of gravel-like material, the idiopathic hypercalciuria persisted after 1 week on a diet containing 2000 mg of sodium and 300 mg of calcium. On the basis of studies that examined the site along the nephron responsible for hypercalciuria in rats with streptozocin-induced diabetes, we speculate that in children with renal glycosuria, there is defective reabsorption of glucose and calcium in the straight portion of the proximal tubule or in the collecting duct. It is likely that a similar mechanism accounts for the idiopathic hypercalciuria in children with diabetes mellitus.
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PMID:Hypercalciuria in children with renal glycosuria: evidence of dual renal tubular reabsorptive defects. 841 May 29

The roles of growth factors in the pathogenesis of various forms of acute and chronic renal disease are largely putative. Nevertheless, there is a growing body of information that links specific growth factors to particular forms of renal injury. In all instances, it is supposed that such associations are not necessarily unique and that multiple cytokines probably interact to determine the pattern of injury or the regenerative response to such injury. Regeneration of tubular epithelium after acute tubular necrosis involves upregulation of the epidermal growth factor (EGF) receptor. Early studies of exogenously administered EGF indicate that the severity and duration of renal failure may be attenuated by this growth factor. Thus far, the observed responses have been limited and the role of EGF as a therapeutic agent requires more study. The mechanism of generation of tubulointerstitial injury in most forms of renal disease is difficult to understand. Early in vitro studies of growth factor production by tubular cells (in the absence of any infiltrating cells) indicate that platelet-derived growth factor produced by the medullary collecting duct is mitogenic for renal medullary fibroblasts, suggesting a paracrine growth system in this region of the kidney. Insulin-like growth factor I has also been shown to be produced by collecting duct cells. Its production is increased by EGF, and its association with certain forms of renal hypertrophy, i.e., diabetes and hypersomatotrophic states, implies its participation in the hypertrophic growth response. Platelet-derived growth factor is a potent mitogen for glomerular mesangial cells, and its production is regulated by a variety of cytokines.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Evolving role of growth factors in the renal response to acute and chronic disease. 159 57

Growth hormone (GH) and insulin-like growth factor I (IGF-I) exert a variety of actions in renal tissue. To shed light upon the renal GH-IGF I axis we have characterized the cell biology of GH and IGF I in two parts of the nephron that are targets for these peptides, proximal tubule and collecting duct. Receptors for both GH and IGF I are present in the basolateral membrane of the renal proximal tubular cell. GH activates phospholipase C and IGF I stimulates phosphorylation of its receptor at this site. Both peptides directly enhance gluconeogenesis in proximal tubule. GH stimulates IGF I gene expression in collecting duct. IGF I of collecting duct origin could act as a paracrine growth factor in other portions of the nephron. IGF I may be causative of renal hypertrophy that occurs in the settings of hypersomatotropism, unilateral nephrectomy (compensatory hypertrophy) and diabetes mellitus.
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PMID:Renal cellular biology of growth hormone and insulin-like growth factor I. 165 79

After summarizing the progress which has been made with regard to the isolation and characterization of homogeneous cell populations from the kidney, a brief survey of current techniques available for the analysis of intracellular parameters is given. Special emphasis is thereby placed on the use of electron probe X-ray microanalysis to determine intracellular elements and on "in vivo" nuclear magnetic resonance to define metabolic pathways in isolated cells. These methods have been applied to study ion and substrate fluxes in isolated collecting duct cells and the response of these cells to changes in osmolality of the extracellular medium. This response involves initially fast water movements accompanied by changes in intracellular sodium and chloride but not potassium concentration. Longterm adaptation is achieved by the adjustment of the intracellular concentration of "organic osmolytes" such as sorbitol, myoinositol, glycerophosphorylcholine, and betaine through changes in the rate of efflux of these metabolites from the cell. In the last section the effect of experimentally induced diabetes mellitus on the osmoregulation in isolated collecting ducts is described.
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PMID:[Study of kidney function using isolated cells]. 217 22

Intracellular accumulation of sorbitol, generated from D-glucose via the aldose reductase pathway, is thought to play an important role in diabetic complications such as lens cataracts and neuropathy. In order to elucidate the effect of diabetes on the renal inner medulla, another sorbitol-rich tissue, male Wistar rats were treated with a single dose of streptozotocin (60 mg/kg body weight, i.p.). Six weeks later total inner medullary tissue (IM) or isolated inner medullary collecting duct (IMCD) cells were prepared. In diabetic IM tissue, sorbitol content was 1.8-fold higher than in control IM tissue (134 +/- 17 vs. 74 +/- 22 mumol/g tissue protein). Sorbitol production in both normal and diabetic IMCD cells was strongly dependent on extracellular D-glucose concentration. In normal cells, for example, sorbitol production was 90 +/- 9 mumol sorbitol/g protein x h at 45 mM D-glucose compared to 13 +/- 1 mumol/g protein x h at 5 mM. At identical D-glucose concentrations sorbitol synthesis in diabetic IMCD cells was, however, always significantly higher than in control cells (122% of control at 15 mM and 126% of control at 45 mM). In addition, aldose reductase activity in diabetic IM was found to be augmented. The maximal velocity was 4.2 times higher (97 +/- 22 U/g protein vs. 23 +/- 7 U/g protein) while the Km of the enzyme remained unchanged. Membrane permeability for sorbitol or the response to changes in extracellular osmolarity was not significantly different in diabetic IMCD cells and normal cells with correspondingly high intracellular sorbitol concentrations. Similarly the kinetic parameters of D-glucose uptake were not altered by streptozotocin treatment.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Sorbitol metabolism in inner medullary collecting duct cells of diabetic rats. 252 20

The effect of streptozotocin-induced diabetes mellitus on rat renal ouabain-sensitive ATPase in six distinct nephron segments was studied. Twenty-four hours after administration of streptozotocin, blood glucose increased threefold (P less than 0.001), and glucosuria was evident. Aldosterone levels increased almost twofold (P less than 0.001). Ouabain-sensitive ATPase increased in the proximal segments PC (proximal convoluted tubule) and PS (proximal straight tubule) by 43 and 62%, respectively, (P less than 0.001) and CD (cortical collecting duct) ouabain-sensitive ATPase increased 77% (P less than 0.001). Ouabain-sensitive ATPase in the cortical (CTAL) and medullary (MTAL) thick ascending limbs of Henle's loop and in the DC (distal convoluted tubule) remained unchanged after 24 h of streptozotocin administration. Eight days after streptozotocin administration, when glomerular filtration rate (GFR) was already markedly elevated, ouabain-sensitive ATPase remained increased in the PC, PS, and CD but was significantly less compared with the activity after 24 h (P less than 0.05), whereas in the CTAL and MTAL a marked increase in ouabain-sensitive ATPase occurred by 54% in the CTAL and 65% in the MTAL (P less than 0.001). Aldosterone levels remained elevated compared with control but less than after 24 h. Pretreatment with deoxycorticosterone acetate abolished the increase in ouabain-sensitive ATPase in the CD. These findings show that streptozotocin-induced diabetes mellitus in the rat is associated with a substantial increase in ouabain-sensitive ATPase activity along most of the nephron. This increase in enzyme activity may represent a mechanism of physiological adaptation of the nephron to maintain electrolyte homeostasis in diabetes in face of the increased GFR and osmotic diuresis.
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PMID:Enhanced renal tubular ouabain-sensitive ATPase in streptozotocin diabetes mellitus. 301 97

To determine whether decreased renal responsiveness to atrial natriuretic peptide (ANP) in diabetes is mediated by alterations in the renal ANP receptor, ANP receptor density and affinity were measured 17-20 d after streptozotocin injection and compared with values in vehicle-treated controls and streptozotocin-treated rats made euglycemic with insulin. Plasma ANP concentration was significantly greater in hyperglycemic diabetic rats than in control or euglycemic diabetic rats. Both in glomeruli and inner medulla, ANP receptor dissociation constant did not differ among the three study groups, whereas the maximum binding capacity was decreased significantly in hyperglycemic diabetics in comparison with controls and euglycemic diabetics. Glomerular clearance receptors were also decreased significantly in hyperglycemic diabetic rats in comparison with control and euglycemic diabetic rats. To determine whether the decreased number of renal ANP receptors in diabetic rats was associated with a decreased biological response, we measured ANP-dependent cyclic GMP (cGMP) accumulation by isolated glomeruli and inner medullary collecting duct cells in vitro. cGMP accumulation was significantly less in hyperglycemic diabetic rats than in controls or euglycemic diabetic rats both in the presence or absence of the phosphodiesterase inhibitor zaprinast. cGMP phosphodiesterase activity in inner medullary collecting duct cells obtained from control and hyperglycemic diabetic rats did not differ. Thus, the decreased number of biologically active ANP receptors in the kidneys of diabetic rats is accompanied by decreased biological responsiveness in vitro and provides a potential explanation for the reduction in renal sensitivity to ANP in this condition.
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PMID:Receptors for atrial natriuretic peptide are decreased in the kidney of rats with streptozotocin-induced diabetes mellitus. 776 90

Streptozotocin diabetes induces a 4-fold increase in the maximal velocity of inner medullary aldose reductase as determined in vitro but increases sorbitol synthesis in intact inner medullary collecting duct (IMCD) cells only 1.3-fold. In order to resolve this discrepancy we investigated the importance of intracellular factors in controlling the role of cellular sorbitol synthesis. These factors include glucose concentration, sorbitol concentration, the activity of the NADPH-regenerating pentose phosphate pathway, intracellular NADP and NADPH content, and intracellular reduced (GSH) and oxidized glutathione (GSSG). It was found that the apparent Km of cellular sorbitol production for glucose was identical in control and diabetic rats (56 +/- 18 vs. 59 +/- 14 mmol/l D-glucose), whereas Vmax increased by 31% in diabetes. In inner medullary collecting duct cells of diabetic rats containing 146 +/- 5 mumol sorbitol/g protein, sorbitol synthesis was slightly lower (-15%), compared to cells which had been sorbitol-depleted prior to the experiment (87 +/- 4 mumol sorbitol/g protein). However, no inhibitory effect of sorbitol (up to 200 mmol/l) was observed on aldose reductase activity in vitro. In diabetic rats the content of NADPH was about 32% lower than in the control rats (3.8 +/- 0.3 vs. 5.6 +/- 0.4 mumol/g protein) and the ratio of NADPH/NADP was decreased from 25.6 +/- 5.1 to 8.6 +/- 1.7. In homogenates of the inner medulla the activity of 6-phospho-gluconate dehydrogenase (EC 1.1.1.43) was identical in both experimental groups, so the pentose phosphate shunt seems to be unaltered. GSH content in diabetic rats was also diminished (4.02 +/- 0.67 mumol/g protein vs. 7.41 +/- 0.5 mumol/g protein) and the GSH/GSSG ratio fell from 92.6 to 57.4. In enzyme tests in vitro an apparent Km of 7.3 +/- 1.9 mumol/l of the aldose reductase for NADPH was found; NADP acted as competitive inhibitor with an apparent K(i) of 183 +/- 31 mumol/l. Aldose reductase activity was also found to be strongly inhibited by the SH-group reagent p-chloromercurybenzoesulfonate (apparent K(i) = 0.85 x 10(-6) mol/l). Combining the results obtained on the properties of the aldose reductase in vitro and the observation made in the intact cells, the investigators suggest that the decrease in NADPH/NADP ratio, as well as changes in the redox state in the cells of diabetic animals, can play a significant role in the control of sorbitol synthesis.
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PMID:Control of sorbitol metabolism in renal inner medulla of diabetic rats: regulation by substrate, cosubstrate and products of the aldose reductase reaction. 824 Dec 88

In situ hybridization was used to map cellular patterns of gene expression for facilitative glucose transporters (GTs) 1-5 in the developing and adult rat kidney. GT3 was not detected. GT1 mRNA was present in the proximal straight tubule (PST), distal nephron and collecting duct. GT2 mRNA was localized in both proximal convoluted and PST, while GT5 mRNA was detected only in the PST. GT4 mRNA and immunoreactivity were focally localized in the thick ascending limb of Henle's loop and were coexpressed with IGF-I. Thus, each of the four different isoforms demonstrated a distinct renal distribution, with GTs 1, 2, and 5 coexpressed in the PST. Renal GT1 and GT5 gene expression were unchanged throughout development, while GT2 was most abundant before weaning and GT4 was first detected after weaning. Only GT4 appeared to be hormonally regulated: It was decreased after hypophysectomy and increased after vasopressin treatment, but was not affected by 1 or 4 d of insulinopenic diabetes mellitus. The coexpression of GT4 and IGF-I in the thick ascending limb segment of the nephron suggests a novel autocrine/paracrine mechanism by which cells may control local fuel economy independently from that of the larger structure to which they belong and from the systemic hormonal milieu.
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PMID:Anatomical and developmental patterns of facilitative glucose transporter gene expression in the rat kidney. 847 19

Pathological accumulations of glycogen were studied in the kidney tubular epithelium in untreated STZ-induced diabetic rats of 50 days diabetes duration. Blood glucose concentrations were approximately 17 mM, and the animals had no ketonuria. At the termination of the experiment, the kidneys were perfusion-fixed, and serial sections were cut from the renal capsule to the tip of the papilla and stained with toluidine blue and periodic acid Schiff. By tracing tubular profiles from section to section in a light microscope, the outlines of nephrons were reconstructed, and abnormal glycogen accumulations were mapped in accordance with the outlines. The exact segmental localization, character, and extension of the glycogen accumulations were determined. The predominant location of the pathological glycogen accumulations was in the thick ascending limb of Henle's loop. Dot-shaped and diffuse-appearing glycogen accumulations were discretely distributed throughout the segment, and large confluent cytoplasmic accumulations of glycogen were also present. On a continuous basis, glycogen was present only in the cortical thick ascending limb of Henle's loop and the macula densa segment excluding the macula densa cells. In the distal convoluted tubule and the cortical collecting duct system, scattered dot-shaped and diffuse glycogen accumulations were discretely distributed. Furthermore, glycogen appeared as confluent, cytoplasmic accumulations in the initial part of the descending thin limb of Henle's loop. In addition, glycogen accumulations were found in nuclei within a narrow stripe of the outer stripe of the outer medulla in the medullary thick ascending limb of Henle's loop.
Diabetes 1993 Jun
PMID:Structure and segmental localization of glycogen in the diabetic rat kidney. 849 12


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