Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P41181 (collecting duct)
 5,183 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Micropuncture studies were performed in rats infused with LiCl to induce stable plasma lithium concentrations of 2--3 mEq/l, or with an equivalent amount of NaCl. In free flow experiments LiCl reduced proximal tubule fractional reabsorption of sodium and potassium. Reduced reabsorption of bicarbonate, as reflected by a decrease in TF/PCl, was also observed. Proximal fractional reabsorption of chloride, however, was not affected. The TF/PIn at the end proximal tubule was 2.6 +/- 0.2 (mean +/- SEM) in controls and 2.1 +/- 0.1 in the experimental animals (P less than 0.025). In the distal portions of the nephron lithium treatment caused a fall in fractional reabsorption of water and sodium, while potassium secretion was stimulated in the distal tubule. Previous studies have indicated that lithium influences antidiuretic hormone stimulated water transport in the collecting duct. These experiments demonstrate that lithium also affects the transport of water and electrolytes in multiple nephron segments, including the proximal and distal convolution.
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PMID:Micropuncture study on the effects of lithium on proximal and distal tubule function in the rat kidney. 56 82

Although clearance studies in man and experimental animals indicate that filtered lithium is reabsorbed primarily in the proximal tubule, it is unclear whether lithium is also reabsorbed in distal portions of the nephron. Micropuncture studies were, therefore, performed to determine the nephron sites involved in lithium transport during free flow. A method was established to estimate the concentration of lithium in nanoliter samples, using the Helium Glow photometer, which permitted the accurate measurement of lithium in tubular fluid samples over a range from 0.5--30.0 mM. Approximately 56% of filtered lithium and tubular fluid was reabsorbed at the end of the proximal convolution, while at the early distal tubule 75% of filtered lithium and water was reabsorbed. There was no change in net transepithelial movement of lithium beyond the loop of Henle. These data suggest that lithium transport is localized to the proximal tubule, including the pars recta. Lithium reabsorption does not occur in distal tubule or collecting duct. Beyond the early distal tubule net movement of lithium and sodium is dissociated.
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PMID:A micropuncture study of the renal handling of lithium. 57 43

Kidney cells of the marine stickleback Spinachia have been studied with histochemical methods for the demonstration of glycoconjugates. The fine structure of epithelial cells is described. Mucus threads in the nephronic tubule of sexually mature consist of neutral glycoprotein which corresponds with the secretory granules in proximal tubule segment II cells. Large lysosome-like inclusions, which also react with PAS, are present in many P II cells. All cells of the collecting duct epithelium differentiate into mucous cells in male Spinachia. The nature of their secretory products, which are well preserved by freeze-drying, is discussed. Sialylated glycoprotein is present in mucus granules and sulphated glycoprotein can be demonstrated at the apex of collecting duct cells. Collecting duct cell mucus can be digested with testicular hyaluronidase indicating that proteoglycans may be involved in the structure of macromolecules. The observations are compared with studies of mucus production in the urinary apparatus of several other vertebrates.
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PMID:The kidney of a teleost, Spinachia spinachia. II. Histochemical identification of sialic acid-containing glycoprotein and fine structure of mucus secreting cells. 58 60

The opisthonephric kidney of juvenile fifteen spined stickleback (Spinachia spinachia (L.)) has been studied by light and electron microscopical investigation. The renal portal system and microcirculation has been demonstrated by casts of coloured plastic Microfil. Glomeruli are well vascularized as revealed by perfusion fixation. They contribute to the formation of urine in collaboration with a proximal tubule segment I that shows resorptive capacity. Epithelial cells of the proximal tubule segment II, which make up the bulk of the nephronic tubular mass are supposed to constitute very active secretory elements. The possible role of mucus secretion in the collecting duct-urinary duct system is discussed. Juxtaglomerulcar cells have been seen in various stages of secretion.
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PMID:The kidney of Spinachia spinachia (L.) Flem. (Gasterosteidae, pisces) 1. Investigations of juvenile sticklebacks: anatomy, circulation and fine structure. 61 97

We conducted experiments to determine (1) tissue, blood, and urine levels of adenosine produced by the ischemic kidney under conditions of renal artery occlusion, and (2) the site(s) of production and release of adenosine by the kidney. Concentrations of adenosine, inosine, and hypoxanthine in the dog urine were found to increase after 2 minutes of renal artery occlusion as were concentrations of these metabolites in renal tissue after 10 minutes of renal artery occlusion. Renal venous plasma levels of inosine and hypoxanthine also were elevated after 3 minutes of arterial occlusion. In modified stop-flow experiments, adenosine appeared in the urine in a peak that corresponded most closely with proximal tubule fluid. 5'-Nucleotidase, the enzyme which catalyzes the dephosphorylation of 5'-AMP or 5'-IMP to adenosine or inosine, respectively, was found to be located primarily on the external membranes and mitochondria of proximal tubule cells, but not in distal tubule or collecting duct cells. Since adenosine has been demonstrated to elicit renal vasoconstriction and is produced by the ischemic kidney, it is suggested that adenosine may be involved in the mediation of postocclusion renal ischemia.
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PMID:Adenosine production in the ischemic kidney. 67 22

The effects of acute unilateral ureteral obstruction (UUO) of 18 h duration on deep nephron function was evaluated in 14 weanling rats with the technique of micropuncture. After release of UUO, 3.4 +/- 0.66% (SE) of the filtered water remained at the tip of the collecting duct nearly fivefold greater than in controls (0.75 +/- 0.10%). Similar differences were seen in fractional sodium that remained at this site. The ratio of tubular fluid osmolality to that of plasma was also reduced in the UUO group (1.53 +/- 0.06 vs. 4.60 +/- 0.26 in controls, P less than 0.001). Single nephron glomerular filtration rate of cortical and deep nephrons was significantly less (P less than 0.001) after release of UUO. Although the percentage of filtering nephrons was significantly reduced in both nephron populations, the decline in glomerular filtration rate was greater in cortical than in juxtamedullary nephrons (cortical:juxtamedullary nephrons = 27.6 +/- 4.5% vs. 53.3 +/- 5.2% in controls, P less than 0.005) which suggests that single nephron glomerular filtration rate is redistributed to deep nephrons after release of UUO. In contrast to cortical nephrons, the amount of tubular fluid which remains near the bend of the loop of Henle of deep nephrons was greater after release of UUO. This appeared to be the result of a decrease in the reabsorption of both water (tubular fluid:plasma inulin = 2.41 +/- 0.16 vs. 7.94 +/- 0.69 in controls, P less than 0.001) and sodium (52.3 +/- 4% vs. 40.7 +/- 2.9% of the filtered sodium in controls, P less than 0.02). It is suggested that this altered reabsorption occurs along both the proximal tubule and descending limb of the loop of Henle of juxtamedullary nephrons. Inner medullary plasma flow (IMPF), as measured with the [125I]albumin-accumulation technique, was significantly depressed before release of UUO, but exceeded control values 90 min postrelease. Such changes imply that the filtration fraction of deep nephrons is decreased and that physical factors in the proximal tubular reabsorption of sodium have been altered. When papillary solute content was measured before release of UUO it was low (428 +/- 23 vs. 1,205 +/- 106 mosmol/kg in controls, P less than 0.001) which indicates that the decline in papillary osmolality is not a consequence of the increased IMPF seen after ureteral release, but rather precedes it. In fact, the decline in papillary osmolality may contribute to the increase in IMPF after release of UUO and to the decreased reabsorption of fluid along the descending limb of the loop of Henle.
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PMID:Deep nephron function after release of acute unilateral ureteral obstruction in the young rat. 74 76

Ultrastructural features of the tubular nephron of the garter snake, with special reference to modifications for conservation of water, were studied using transmission electron microscopy, freeze-fracture and tracer experiments. Although a nephric loop (loop of Henle) is lacking, the tubules appear to be structurally well adapted for efficient ion and water reabsorption. The most prominent features are well developed microvilli in the proximal tubule and elaborate latteral folds, particularly in the distal tubule and collecting ducts. The latter structures are highly interdigitated, creating complex intercellular channels, perhaps facilitating transepithelial fluid transport. Only the proximal tubule actively absorbs and degrades protein tracers from the lumen. The cells of the collecting duct secrete mucus which may precipitate and bind urate salts in the lumen. This may be significant in the excretion of these salts, a process which combines maximal removal of salts and nitrogenous wastes with minimal loss of water.
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PMID:Ultrastructure of the tubular nephron of the garter snake Thamnophis sirtalis. 76 Apr 86

Histochemical and immuno-histochemical studies on kidney sections of adult rats and rats at different stages of development were carried out to estimate enzyme concentrations in nephron segments. Aminopeptidase and alkaline phosphatase were found from 3 days before birth in proximal tubule cells, aldolase-B and aldolase-A in all the nephron and collecting duct. The concentration of the enzymes remained remarkably constant from the 3rd day after birth onwards, except for aldolase-A in the distal tubule cells. The concentration of aldolase-B was higher than of aldolase-A in the distal tubule cells. The concentration of aldolase-B was higher than of aldolase-A, in glomerula and proximal tubules, that of aldolase-A was higher than that of aldolase-B in the ascending thick part of the Henle loop and in the following parts of the nephron. This implies that the concentration of the enzymes is the limiting factor for the regulation of substrate hydrolysis and that the nephron when formed can function as efficiently as the nephron of the adult rat with respect to these enzymes.
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PMID:Aspects of regulation in kidney at the enzymic level: aldolase isozymes, aminopeptidase and alkaline phosphatase. 79 83

The stop-flow technique was used in dogs to determine the site of entry of urinary prostaglandins (PG) into tubular fluid. The proximal tubule was localized by the peak (U/PPAH)/(U/PIn) and the distal tubule and collecting duct by the peak U/PIn and the minimum (U/PNa)/(U/PIn). The peak of prostaglandin E (PGE) concentration was located 4.8+/-0.8 (SEM) ml distal to the proximal tubule and 4.6+/-0.8 (SEM) ml proximal to the distal nephron. At its peak, PGE was concentrated 6.3-fold over baseline, whereas inulin was concentrated 1.4-fold at its peak. The height of the PGE peak but not its location was increased by an i.v. infusion of angiotensin II at 20 ng/kg of body wt per min. Indomethacin abolished the PG peak. In a single experiment, prostaglandin F2alpha (PGF2alpha) exhibited an excretion pattern similar to PGE. These data indicate that the site of entry of PG into tubular fluid is most likely in the loop of Henle. This is consistent with the hypothesis that PG synthesized in the medulla can be transported to the cortex via tubular fluid. Whether PG in the tubular fluid can influence renal function remains to be determined.
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PMID:Urinary prostaglandins: site of entry into renal tubular fluid. 85 73

The effects of acute bilateral ureteral obstruction (BUO) of 18-h duration on deep nephron and collecting duct function were studied by micropuncture in 11 weanling rats. After release of BUO glomerular filtration rate was reduced (178+/-15 vs. 1,343+/-119 mul/min per g kidney weight in shams), while urine flow was increased averaging 17.5+/-1.3 vs. 6.8+/-0.72 mul/min per g kidney weight in controls. There was a marked increase in the absolute and fractional excretion of Na. Single nephron glomerular filtration rate of deep nephrons was reduced in the BUO group, mean 19.4+/-3.5 vs. 77.0+/-7.7 nl/min per g kidney weight in shams. Single nephron glomerular filtration rate of superficial nephrons fell to the same extent after relief of BUO. Mean tubular fluid to plasma inulin ratio of fluid from Henle's loop was 2.46+/-0.20 after relief of BUO vs. 8.23+/-0.85 in shams. This suggested a reduction in the reabsorption of Na and water before the bend of the loop of Henle, most likely in both the proximal tubule and descending limb. Fluid osmolality was depressed due to a decline in both Na and nonelectrolyte solute content. After release of BUO the percentage of filtered water remaining in the collecting duct (CD) at the base of the papilla was greater than in controls (13.3+/-2.0 and 1.72+/-0.01%, respectively) but fell significantly by the tip of the papilla to 7.92+/-1.12 vs. 1.17+/-0.02% in controls. These results indicate that water was reabsorbed along the terminal CD after relief of ureteral obstruction. In fact, a greater fraction was reabsorbed in this segment after release of BUO (5.37+/-1.58%) than after sham operation (0.55+/-0.15%). Similar changes were seen in Na excretion. Thus alterations in deep nephron function appear to contribute to the natriuresis and diuresis which follow release of BUO while terminal CD function in this model appears intact.
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PMID:Effects of acute bilateral ureteral obstruction on deep nephron and terminal collecting duct function in the young rat. 86 2


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