Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
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.
 ...
PMID:Micropuncture study on the effects of lithium on proximal and distal tubule function in the rat kidney. 56 82

Functionally isolated segments of rat colon and rectum were perfused in situ in a closed loop system. Rectum was defined as the lower 25--35% of the length of large intestine (cecum excluded). Perfusion conditions were optimized at 0.5 ml.min-1 and 3 cm H2O luminal pressure. Variation of perfusion rate between 0.2 and 2 ml.min-1 did not influence net volume transport (JNV). Luminal distension following elevation of hydrostatic pressure to 18 cm H2O reversibly increased Jnv. Under control conditions Jnv and Na+-transport rates (JnNa) of colon were 2--3 times higher than those of rectum. In colon transepithelial electrical potential difference (psims) was time independent --12 mV (lumen negative) whereas rectal psims increased with time from --6 mV, reaching a plateau of --67 mV within 6 h. Amiloride 10(-4) mol.l-1 had no effect on psims, Jnv, and JnNa in colon but did slightly depress K+-secretion in colon descendens. In contrast, psims in rectum was dose-dependently depressed, being reversed to +7 mV at 10(-4) mol.l-1. Jnv and JnNa were decreased by half. Acetazolamide in addition to amiloride lowered the positive post-amiloride rectal psims by half. Adrenalectomy had no effect on colonic psims, but abolished psims of the rectum. A single dose of 40 microgram.kg-1 b.w. aldosterone during the experiment restored the typical time course of rectal psims, but did not affect psims in colon. It is concluded that aldosterone induces an amiloride-sensitive Na+-pathway only in rectum, but not in colon, and that colon and rectum differ basically in their transport properties, quantitatively as well as qualitatively, as do the kidney distal convoluted tubule and the cortical collecting duct.
 ...
PMID:Segmental heterogeneity of epithelial transport in rat large intestine. 56 27

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.
 ...
PMID:A micropuncture study of the renal handling of lithium. 57 43

1. The diffusional permeabilities of collecting duct membranes to THO, 14C-urea and 22Na+ have been measured at different concentrations of urea, NaCl and mannitol. 2. In the absence of urea in perfusate and bath or in its presence in low concentrations, the diffusional permeability to urea was 2.0 (s.e.m. = 0.15, n = 58) micrometer s-1, compared with 0.87 (s.e.m. = 0.06, n = 29) microgram s-1 when 200 mmol/l urea was present. The permeability of the collecting ducts to THO or Na+ was not affected by the different urea concentrations. 3. High concentrations of sodium chloride increased the diffusional permeability of collecting ducts to water and urea but did not affect the diffusional permeability of the collecting duct to Na+. 4. Mannitol had effects similar to those of sodium chloride. 5. In all media tested there was an increase in THO and urea permeability when supramaximal amounts of antidiuretic hormone were added. The increases in the various media for each substance were similar, despite widely different starting permeabilities. 6. The results suggest that solutes and water move across collecting duct epithelium by several pathways that respond differently to various stimuli.
 ...
PMID:The effects of sodium chloride, urea and mannitol on the permeability in vitro fo rat papillary collecting ducts to THO, 14C-urea and 22Na. 58 72

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.
 ...
PMID:Deep nephron function after release of acute unilateral ureteral obstruction in the young rat. 74 76

In anaesthesized dogs given large doses of ADH and DOC and subjected to acute left renal denervation, urine flow (V) and sodium excretion (UNaV) rose significantly in response to bilateral carotid artery clamping in both the intact (p less than 0.05) and the denervated kidney (p less than 0.001). This was associated with significant (p less than 0.05) increases of the tubular rejection fraction of sodium (TRFNa) while creatinine clearance (Ccr) remained unchanged. Following a second control period, carotid occlusion was repeated, while perfusion pressure in the left kidney was kept constant by aortic constriction. In this case the diuretic and natriuretic response in the right kidney occurred in the same fashion as previously, and no significant change in V, UNaV, or TRFNa was observed in the left kidney. The amount of free water reabsorbed in the collecting duct (TcH2O) was not consistently altered by carotid occlusion. It is concluded that acute renal denervation augments the pressure diuresis that follows carotid occlusion. The failure of carotid polyuria to occur when renal perfusion pressure is kept constant points to the importance of mechanical factors. Still, a wash-out of the medullary osmotic gradient seems to be an unlikely mechanism.
 ...
PMID:Mechanism of carotid-occlusion diuresis. 75 93

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.
 ...
PMID:Ultrastructure of the tubular nephron of the garter snake Thamnophis sirtalis. 76 Apr 86

The effect of tubular obstruction on renal function has been understood poorly at the tubular level and from the clinical standpoint. In our review the evidence for a direct influence of hydrostatic pressure on tubular transport and glomerular filtration is examined. The data generated to date indicate a direct influence of hydrostatic pressure on tubular transport only at the level of the distal convoluted tubule and collecting duct. With respect to glomerular filtration increased tubular pressure reduces the net driving force for filtration and reduces glomerular filtration rate in the absence of a compensatory increase in glomerular hydrostatic pressure. We next review physiological data concerning the mechanism of post-obstructive diuresis. Available information suggests 4 factors that play a significant role in the clinical syndrome of post-obstructive diuresis: 1) medullo-papillary washout, 2) decreased fractional and absolute salt and water reabsorption in the collecting duct, presumably secondary to direct influence of hydrostatic pressure on transport mechanisms, 3) osmotic diuresis secondary to retention of urea and other osmotic solutes during the period of obstruction and 4) prior salt and water administration in the absence of excretion, resulting in extracellular fluid volume expansion.
 ...
PMID:The influence of increased tubular hydrostatic pressure on renal function. 77 39

In a previously nephrectomized patient with a well functioning renal allograft, acute renal failure with massive polyuria and hypertension developed. Relief of a periureteric obstruction resulted in rapid correction of all three. Pathogenesis of hypotonic polyuria is thought to be a defect in the collecting duct permeability to water, stimulating nephrogenic diabetes insipidus. Normal urinary dilution and acidification suggest intact function of the ascending loop of Henle and distal convoluted tubules. The quick reversal of polyuria and renal failure after obtaining relief of the obstruction suggest that both the decrease in the glomerular filtration rate and tubular dysfunctions are due to functional changes in the nephron rather than to organic damage, a possibility also borne out by the findings in a renal biopsy specimen showing normal glomeruli and intact tubular epithelial cells. Ureteric obstruction should be considered in any patient with renal failure and polyuria; it may be a correctable cause of hypertension.
 ...
PMID:Obstructive polyuric renal failure following renal transplantation. 79 85

Inappropriate polyuria leading to hypovolemia and hypotension occurs frequently in severely septic patients. It's etiology was studied in three patients with polyuria and systolic hypotension. Glomerular filtration rate and renal blood flow were measured by the standard renal clearance techniques. Renal blood flow distribution to the outer cortex, inner cortex-outer medulla, and the inner medulla were measured by radioactive xenon. The glomerular filtration rate, renal blood flow, and renal blood flow distribution were normal. Polyuria does not result from a maldistribution of renal blood flow. Antidiuretic hormone did not alter the polyuric syndrome. These data suggest that sepsis produces a blockade at either the distal tubule or the collecting duct, thereby preventing salt and water conservation. This blockade may be due to either a toxin or a toxic metabolic breakdown product of sepsis.
 ...
PMID:Mechanism of inappropriate polyuria in septic patients. 84 54


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>