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)

In this study we extend the analysis of the preceding two studies [J. L. Stephenson, J. F. Jen, H. Wang, and R. P. Tewarson. Am. J. Physiol. 268 (Renal Fluid Electrolyte Physiol. 37): F698-F709, 1995; and J. F. Jen, H. Wang, R. P. Tewarson, and J. L. Stephenson. Am. J. Physiol. 268 (Renal Fluid Electrolyte Physiol. 37): F000-F000, 1995] to a model that includes vasa recta. Distribution of nephron and vasa recta lengths is represented by shunting from descending to ascending flow. It is found that the effect of radial separation of structures on concentrating ability is closely linked to vasa recta flow. With minimal or no vasa recta flow the extent of radial mixing has little effect on concentrating ability. As vasa recta flow increases, concentrating ability is decreased by radial mixing. Convective uphill transport of NaCl is again observed, but concentrating ability appears to depend primarily on urea delivery to the inner medulla from the collecting duct rather than on the mechanism of salt transport out of thin ascending limb. Central core models give an upper bound on concentrating ability but do not attain the maximum urine osmolality of the rat with experimental values of tubular permeabilities.
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PMID:Effect of vasa recta flow on concentrating ability of models of renal inner medulla. 773 27

Hormonal activation of protein kinase C (PKC) is a major signaling mechanism regulating salt and water transport in the distal nephron. We used antisense DNA to down-regulate a PKC isoform in the rabbit cortical collecting duct (CCD) and examined its role in mediating arginine vasopressin's (AVP) effect on salt transport in the CCD. Immunoblots demonstrate that PKC-epsilon (diacylglycerol sensitive) and PKC-zeta (diacylglycerol insensitive) are the major PKC isoforms in both freshly isolated and primary cultures of rabbit CCDs. Rabbit CCDs grown on semi-permeable supports, displayed a positive baseline short circuit current (Isc), which was abolished by amiloride, demonstrating active Na+ absorption. Both AVP and 8-chloro-phenylthio-cAMP (8CPTcAMP) transiently increased Isc, however, within 40 min Isc fell below baseline. Down-regulation of PKC-epsilon, as confirmed by immunoblot, was achieved either by treatment with a PKC-epsilon-specific antisense oligonucleotide or 48 h of 1 microM PMA. In PKC-epsilon down-regulated cells, 8CPTcAMP produced a sustained, rather than transient, increase in Isc. We suggest cAMP stimulates Na+ transport, but secondary activation of PKC-epsilon results in the sustained inhibition of Na+ transport seen in response to vasopressin in the CCD.
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PMID:Anti sense DNA down-regulates proteins kinase C-epsilon and enhances vasopressin-stimulated Na+ absorption in rabbit cortical collecting duct. 776 15

A 30-y-old female presented with a history of hypertension and a modest degree of hyperkalemia. There was a mild degree of contraction of her ECF volume on clinical examination, with elevated levels of renin and aldosterone in plasma. No causes for secondary hypertension were found. Laboratory investigations revealed a slightly reduced glomerular filtration rate (GFR) and a subnormal kaliuretic response to exogenous mineralocorticoids. When a further degree of ECF volume contraction was induced, she was unable to conserve Na+ and Cl- appropriately. Moreover, expansion of the ECF volume led to a significant suppression of the levels of both renin and aldosterone in plasma. We speculate that these findings could be explained by a diminished net rate of reabsorption of Na+ in the cortical collecting duct. Such a reduction could lead to a diminished generation of an electrical gradient to favour the net secretion of K+ and lead to hyperkalemia with renal salt wasting. The resultant contraction of the extracellular fluid volume with the release of renin and aldosterone (and probably other vasoactive hormones) might have predisposed her to hypertension. This hypothesis was supported by the finding that NaCl supplements led to a significant drop in her blood pressure. This case could represent a new syndrome of hyperkalemia and "salt sensitive" hypertension.
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PMID:Hyperkalemia with mild ECF volume contraction: studies to provide a possible physiologic interpretation. 786 45

1. Chronic reduction of salt intake can reduce the natriuretic effect of exogenously administered atrial natriuretic factor. The purpose of this study was to elucidate the intrarenal site(s) of such atrial natriuretic factor resistance. Renal clearance and collecting duct microcatheterization experiments were made before and during infusion of atrial natriuretic factor in three groups of rats: group 1 consisted of rats fed a high salt diet (8% NaCl) for 1 week before the experiment; group II were fed a low salt diet (< 0.008%); group III received the same low salt diet, but were acutely replenished with salt at the time of experiment. 2. Baseline sodium chloride excretion was 6480 +/- 810 nmol min-1 g-1 kidney weight in group 1 compared to 99 +/- 16 in group 1. Fractional reabsorptions in the medullary collecting duct were 37 +/- 6% and 95 +/- 2% of delivered load, respectively (P < 0.05). The fractions of filtered sodium remaining at the beginning of the medullary duct were 6.6 +/- 1.0% of filtered load in group 1 and 2.7 +/- 0.7% in group II (P < 0.05), indicating increased tubular reabsorption in group II, not only in the medullary duct, but also in upstream nephron segments.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Dietary salt extremes and renal function in rats: effect of atrial natriuretic factor. 787 40

Pregnancy in the rat is accompanied by enhanced reabsorption of salt and water throughout most, if not all, of the gestational period. Many mechanisms have been suggested but definitive answers are still awaited. The major area of controversy centres around the detection of changes at term. There is general agreement that, at least in mid-gestation, the increase in reabsorption can be attributed to increases in the proximal tubules, the loop of Henle and the collecting duct. The contribution of the proximal tubule to the increased reabsorption at term is still uncertain. Enhanced salt and water reabsorption is demonstrated in distal nephron segments irrespective of the stage of gestation. Micropuncture and microperfusion experiments have identified increased reabsorption of water, sodium and chloride in the loop of Henle, but it appears that there is net addition of glucose, urea and potassium to the tubular fluid in this segment which, at least for potassium and glucose, offsets to some extent increased reabsorption by the proximal tubule. Altered renal handling of other solutes (uric acid, calcium and magnesium) also occurs throughout pregnancy but the mechanisms responsible and nephron sites involved remain to be investigated. Attempts to attribute altered reabsorption to direct renal effects of changes in maternal hormones are inconclusive. Prolactin mimics some of the pregnancy-associated increases in reabsorption following chronic administration to male and non-pregnant female rats. These effects might be due to a direct renal action of the hormone or even to the volume expansion following its dipsogenic action.
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PMID:Renal tubular function in the gravid rat. 792 8

Studies were conducted to determine whether the cortical collecting duct (CCD) of the Dahl salt-resistant rat (inbred Rapp strain; R/Jr) exhibits the same responses to deoxycorticosterone (DOC; 2.5 mg as a depot injection in vivo, 3-8 days before experimentation) and arginine vasopressin (AVP, 220 pM in vitro) as the Sprague-Dawley (SD) [L. Chen, S.K. Williams, and J.A. Schafer. Am. J. Physiol. 259 (Renal Fluid Electrolyte Physiol. 28): F147-F156, 1990] and Dahl salt-sensitive (inbred Rapp strain, S/Jr) [C.T. Hawk and J.A. Schafer. Am. J. Physiol. 260 (Renal Fluid Electrolyte Physiol. 29): F471-F478, 1991] CCD. Qualitatively, the R/Jr CCD responded as in the other two strains: AVP elevated the osmotic water permeability (Pf, micron/s) from 0 to approximately 1,200; either AVP or DOC, when used alone, increased the lumen-to-bath 22Na+ flux (Jl-->b, pmol.min-1.mm-1) from the control range of 20-25 to approximately 40 and hyperpolarized the transepithelial voltage. AVP and DOC effects were synergistic, elevating Jl-->b to 90 +/- 5 (mean +/- SE) with both hormones, but this value was significantly lower than observed previously in both the SD and the S/Jr CCD, 125 +/- 6 and 140 +/- 6, respectively. However, bath-to-lumen fluxes (Jb--l) were also significantly lower than observed in the SD and S/Jr CCD. Because net fluxes (Jnet) in these experiments can be determined only as nonpaired differences between unidirectional fluxes, it is uncertain whether Jnet values in the R/Jr CCD are significantly lower than in the SD or S/Jr CCD.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Sodium and water transport in cortical collecting duct of Dahl salt-resistant rat. 794 56

Ureteral obstruction causes impaired salt wastage and K+ secretion in the distal nephron segments, including the cortical collecting duct (CCD). Recently, we demonstrated that conductances of Na+ and K+ in the apical membrane, as well as the electrogenic Na(+)-K+ pump activity and the relative K+ conductance in the basolateral membrane of the collecting duct cell, were inhibited in the obstructed kidney after unilateral ureteral obstruction (UUO). To examine whether the increased intrarenal pressure might be causally related to these abnormalities in the CCD, the effects of unilateral renal decapsulation, a maneuver that partially blocks the increase in renal pressure, were evaluated with microelectrode techniques in isolated CCDs from UUO and sham-operated (control) rabbits 24 h after operation. Renal decapsulation had no effects on barrier voltages and conductances in the CCD from control animals. The lumen-negative transepithelial (VT) and basolateral membrane (VB) voltages as well as the transepithelial (GT) and the apical membrane (GA) conductances were decreased in the CCD from UUO animals compared with control animals. Pretreatment of renal decapsulation partially corrected the decreases in VT, VB, GT, and GA seen in the CCD from UUO animals. The changes in apical membrane voltage and GT upon addition of luminal amiloride and Ba2+, and the changes in VB upon addition of bath ouabain, were also decreased in the CCD from UUO animals compared with control animals. Pretreatment of renal decapsulation also partially corrected the above abnormalities seen in UUO animals, whereas it had no effect in control animals. The transference numbers for Cl- (tCl) and K+ (tK) in the basolateral membrane were, respectively, increased and decreased in the CCD from UUO animals compared with control animals. Pretreatment of renal decapsulation also partially corrected the changes in tCl and tK seen in UUO animals, whereas it had no effect in control animals. We conclude that, in UUO animals, renal decapsulation partially corrects the inhibition of apical Na+ and K+ conductances as well as basolateral Na(+)-K+ pump activity and relative K+ conductance seen after UUO, whereas in control animals it has no effect. The increased renal pressure may partly contribute to the defects in Na+ and K+ transport in the CCD from obstructed kidneys. Renal decapsulation has protective effects on impaired Na+ and K+ transports in the CCD after ureteral obstruction.
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PMID:Electrical properties of the rabbit cortical collecting duct from obstructed kidneys after unilateral ureteral obstruction. Effects of renal decapsulation. 796 30

The effect of crude extract of roots of Bredemeyera floribunda Willd., Polygalaceae used by Brazilian popular medicine as a potent diuretic, on renal function in antidiuresis or water diuresis in rats, was studied. During intravenous infusion of the extract (0.05 mg/min/100 g), mean arterial pressure did not change significantly but urine flow, glomerular filtration rate, fractional water and sodium excretion and solute clearance increased significantly, in both groups of animals. In antidiuresis rats the extract significantly increased reabsorption of water by the collecting duct and in water diuresis animals the extract significantly increased free water clearance. Our findings indicate a direct effect of extract on glomerular filtration rate, possibly by detergent like interactions with structural components of glomerular membranes and/or by decreasing renal perfusion pressure. The study on the concentrating and diluting mechanisms suggests preferential action of extract in the proximal tubular cells, possibly on the (Na(+)-K+)-ATPase countertransport system and/or on other proteins components of tubular cell membranes involved with salt transport mechanisms.
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PMID:Effect of crude extract of roots of Bredemeyera floribunda Willd. II. Effect on glomerular filtration rate and renal tubular function of rats. 799 Apr 95

The regulation of transport in the collecting duct is under multi-hormonal control. Vasopressin stimulates water and cation transport, primarily through a V2/Gs-coupled receptor that activates adenylyl cyclase, which raises cAMP. These stimulatory effects are damped by the action of several hormones, including vasopressin itself, which activate inhibitory G proteins, stimulate phospholipid breakdown, increase prostaglandin production, raise intracellular Ca2+, activate protein kinase C, stimulate tyrosine kinases, and raise cGMP. These inhibitory signals interact with the stimulatory, cAMP-coupled signaling pathway at multiple levels. The balance between these pathways controls net salt and water transport in the collecting duct.
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PMID:Hormonal signaling and regulation of salt and water transport in the collecting duct. 801 Jul 58

Previous studies have shown that salt depletion enhances the susceptibility of the kidney to nephrotoxins (amphotericin, cyclosporine, and contrast). To study the renal response to salt depletion, Sprague-Dawley rats were fed a sodium-deficient diet (N = 12) with pair-fed controls (N = 13) for 4 wk. In addition, rats from each group underwent 24-h water deprivation studies (N = 9; four salt deprived, five normal). Plastic 1-micron horizontal sections of mid-inner stripe were examined, and cross-sectional areas of the medullary thick ascending limb (mTAL) were analyzed. The mTAL of the salt-deprived rats were smaller (P = 0.04) and showed greater variance in size (P = 0.02) than control (618 +/- 106 versus 693 +/- 50 microns2). However, mean glomerular and collecting duct cross-sectional areas were unaffected by salt intake. Cross-sectional areas of long- and short-loop mTAL were significantly different, regardless of group (518 +/- 78 versus 732 +/- 92 microns2). Maximal urinary concentrating ability was found to correlate with mTAL cross-sectional area (r = 0.85; P = 0.004) and with long-loop mTAL size (r = 0.77; P = 0.016). However, it did not significantly correlate with short loop mTAL size (r = 0.53; P = 0.14).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effects of salt depletion on the kidney: changes in medullary oxygenation and thick ascending limb size. 802 27


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