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

In vitro studies of isolated, perfused, cortical collecting tubules have demonstrated that prior chronic deoxycorticosterone acetate (DOCA) treatment increases sodium reabsorption in this nephron segment, yet sodium balance in vivo is maintained. To evaluate the effect of chronic DOCA treatment on collecting duct sodium reabsorption in vivo, we compared fractional sodium delivery (FD(Na)%) out of the superficial late distal tubule with the fraction of sodium remaining at the base and the tip of the papillary collecting duct during extracellular fluid volume expansion in untreated, salt-treated, and DOCA-salt-treated rats. In untreated rats, FD(Na)% to the distal tubule was 6.5+/-1.0%, and to the base was 8.7+/-1.6% (Delta2.2+/-0.9%, P < 0.05). FD(Na)% to the tip was 4.9+/-1.1%, significantly less than FD(Na)% to the base (Delta3.7+/-1.1%, P < 0.01). In salt-treated rats, FD(Na)% to the distal tubule was 8.3+/-0.8%, and to the base was 10.4+/-1.1%. FD(Na)% to the tip was 5.9+/-0.6%, significantly less than FD(Na)% to the base (Delta 4.6+/-1.0%, P < 0.005). In DOCA-salt-treated rats, FD(Na)% to the distal tubule was 16.1+/-2.6% and to the base was 9.5+/-1.9% (Delta 6.6+/-1.7%, P < 0.005). FD(Na)% to the tip was 5.9+/-1.2%, also significantly less than FD(Na)% to the base (Delta 3.6+/-1.1%, P < 0.01). We conclude that (a) in DOCA-salt-treated rats, sodium delivery to the end of the superficial distal tubule is greater than in untreated or salt-treated rats; (b) in DOCA-salt-treated rats, sodium delivery to the end of the superficial distal tubule is greater than to the base of the papillary collecting duct, suggesting stimulation of sodium reabsorption in the cortical and(or) outer medullary collecting duct; and (c) sodium reabsorption by the papillary collecting duct is unaffected by chronic DOCA-salt treatment in the volume-expanded rat.
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PMID:Collecting duct sodium reabsorption in deoxycorticosterone-treated rats. 42 50

The hamster renal pelvis has been studied by means of low-power light microscopy, scanning electron microscopy and morphometric analyses. The results of this study are highly suggestive that the contact of pelvic urine with the other medulla as well as with the inner medulla may be an important aspect of final urine formation. The outer medulla constituted nearly 50% of the total pelvic surface area, with the inner stripe of the outer medulla more than twice the pelvic surface area of the outer stripe of the outer medulla. The large outer medullary pelvic surface area was accounted for by the elaboration of the upper pelvic walls into peripelvic columns, opercula ("secondary pyramids"), fornices and secondary pouches. A thin simple-squamous to low cuboidal pelvic epithelium separated pelvic urine from outer medullary parenchyma. The inner medulla which constituted about one quarter of the total pelvic surface area was covered by a cuboidal to columnar pelvic epithelium which appeared morphologically similar to the papillary collecting duct epithelium. Tubules and capillaries of the inner medulla did not appear as closely juxtaposed to the pelvic epithelium as did those of the outer medulla. Cortical tissue comprised only 11.7% of the total pelvic surface area and was covered by transitional epithelium similar to that of ureter and bladder. The previously reported impermeability of this epithelium suggests that pelvic urine contact with the cortex is unimportant in final urine formation. The rich layer of smooth muscle under the transitional epithelium probably functions to move urine into and out of the pelvis during pelvic peristalsis, which has been observed in vivo.
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PMID:Anatomy of the renal pelvis in the hamster. 43 85

The distribution and activities of several oxidative enzymes in the urinary apparatus of five freshwater fish species (river lamprey, lobe finned eel, Prussian carp, rainbow trout and three-spined stickleback) have been studied. Species were selected from three main taxonomic groups: Cyclostomata, Polypterini, Teleostei. Distinctly positive enzyme reactions were only found in the tubular elements of the kidney and the collecting duct-archinephric duct system, with the exception of the generally weak staining intensities of lactate dehydrogenase. The distal tubule normally showed strong to very strong reactions for most of the enzymes investigated. In the epithelial cells of the collecting tubule-collecting duct system, stronger reactions were observed for most of the mitochondrial-bound enzymes, especially succinate dehydrogenase and NADH-diaphorase. For these enzymes, the cells of the archinephric duct reacted strongly positive in Lampetra, Carassius and Gasterosteus. The enzyme patterns of various types of urinary tubules and ducts are compared with results of several morphological studies. In addition, the histochemical findings are discussed in relation to kidney function in different vertebrate groups.
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PMID:Oxidative enzymes in the urinary apparatus of several freshwater fishes. 43 99

Juxtamedullary (JM) nephron and collecting duct function was studied after a two-thirds reduction in renal mass in the young rat. The glomerular filtration rate of JM nephrons was twofold greater in the remnant kidney (RK) group than in controls, but this increase was proportional to the increase measured in surface nephrons. Despite an increase in absolute reabsorption, delivery of sodium and water to the end of the proximal tubule of superficial nephrons and to the bend of Henle's loop of JM nephrons was increased. This was a consequence of an increase in filtered load and a decrease in fractional reabsorption. Potassium handling in surface nephrons was similar to that of sodium and water. In deep nephrons of the RK group, potassium delivery to the bend was increased as a consequence of increased filtered load. The terminal portion of the collecting duct has a role in this adaptive response to a reduction in renal mass. In rats with a RK, reabsorption of water occurred along this segment; however, when the amount reabsorbed was related to delivery, fractional water reabsorption was only 30% of controls. Changes in sodium handling were more profound. In the group with the RK, sodium reabsorption was not detectable along this segment. Thus, while 40% of delivered sodium was reabsorbed in controls, in the remnant kidney group the mean was not different from zero (-1.7%).
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PMID:Response of deep nephrons and the terminal collecting duct to a reduction in renal mass. 44 83

Dogs are frequent subjects in experimental studies of renal physiology and pathology in spite of the paucity of information on their normal renal morphology. In this study, gross morphology, light microscopy, and scanning and transmission electron microscopy were used to describe dog renal anatomy. The dog has a multilobed kidney with the medulla fused into an elongate crest and a renal pelvis of elaborate shape. The outer zone of the medulla lacks a definitive outer stripe. The proximal tubule consists of four distinct anatomical segments. Dark cells are abundant in the collecting duct of the inner medulla. The majority of the nephron segments demonstrate remarkable similarities to those of the human kidney and less to those of the kidney of the laboratory rat.
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PMID:Survey of the morphology of the dog kidney. 44 63

Recently the assumed structural and functional homogeneity of the collecting duct (CD) has been questioned. The objective of this study was to determine if heterogeneity occurs in luminal surface membrane structure or in cytoplasmic configuration of cells in the collecting duct or both. Straight segments of cortical and medullary CD were examined in perfusion-fixed rabbit kidneys with scanning electron microscopy (SEM), light (LM) and transmission electron microscopy (TEM). Principal cells were the most abundant cells in all CD regions; intercalated cells comprised 37% of the cell population on the cortex, 18% in the outer medulla, and less than 1% in the inner medulla. SEM revealed two surface patterns among the ciliated principal cells: 1, located in the cortex and outer medulla, with few surface microvilli, and 2, located in the inner medulla, with abundant microvilli. Intercalated cells exhibited four distinctive luminal surface configurations: I, numerous short microvilli; II, both short and elongate microvilli; III, microplicae alone; and IV, both microvilli and microplicae. Intercalated cells with patterns I and II were predominant in the cortex, while cells with patterns III and IV were most common at the corticomedullary junction. TEM confirmed that marked variation existed in cytoplasmic structures of both principal and intercalated cells. These findings may either indicate the presence of several specific types of principal and intercalated cells or reflect different functional states of the principal and intercalated cells. Regardless of their significance, their presence must be considered in studies seeking to establish precise structural-functional relationships in this region of the rabbit renal tubule.
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PMID:Morphology of rabbit collecting duct. 46 86

We characterized renal tubular reabsorption before and during acute expansion in anesthetized 12-wk-old spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). Although mean arterial pressure was higher in euvolemic, nondiuretic SHR than in WKY, 158 vs. 114 mmHg, kidney and nephron glomerular filtration rate (GFR) as well as fluid reabsorption by the proximal convoluted tubule, loop of Henle, and distal convoluted tubule-collecting duct were similar. In euvolemic SHR with aortic constriction (SHR-AC), an acute decrease in renal perfusion pressure to 114 mmHg reduced sodium and water excretion. Kidney and nephron GFR and fluid reabsorption by segments along the nephron resembled values for SHR and WKY. Infusion of isotonic saline (3 ml.100 g body wt-1.h-1) produced similar increases in fractional sodium and water excretion by SHR and WKY, whereas SHR-AC exhibited a blunted natriuresis and diuresis. During expansion, fluid reabsorption by the nephron segments did not differ appreciably among the three groups. The effect(s) of perfusion pressure on reabsorption by superficial nephrons may be covert and was not unmasked, or may be manifested preferentially by deeper nephrons. We conclude that kidneys of SHR require a higher arterial pressure than kidneys of WKY to excrete a given amount of salt and water.
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PMID:Renal tubular reabsorption in spontaneously hypertensive rats. 46 59

The question of phosphate transport along the collecting duct remains controversial inasmuch as no data from direct in vivo evaluation of this nephron segment have been reported. We measured net phosphate transport along the inner medullary collecting duct (IMCD) using the collecting duct microcatheterization technique in five groups of rats. In control rats no net phosphate transport was found and 9.4% of the fraction of filtered phosphate (FFP) entered the IMCD and was excreted. After acute thyroparathyroidectomy (TPTX) there was a striking reduction in the FFP entering the IMCD, 1.8%, and significant reabsorption occurred, 0.5% being excreted. With acute TPTX and parathormone infusion, delivery increased to 33% without significant change along the IMCD. With acute TPTX and phosphate infusion, delivery was increased to control levels but no change was found in net phosphate transport. In rats studied 5-7 days after uninephrectomy alone, phosphate delivery was greater than in control, 25%, and no net phosphate transport was found. These studies demonstrate that phosphate absorption occurs along the IMCD in acutely TPTX rats when the delivery of phosphate to the IMCD is markedly reduced. The increase in phosphaturia which occurs after a reduction in renal mass cannot be accounted for by changes in net phosphate transport along the IMCD.
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PMID:Phosphate transport along the inner medullary collecting duct of the rat. 46 60

A model of the renal medulla is formulated, taking into account the transport properties of each medullary structure. Using known data on inflow to the vascular and tubular systems and on urine output in normal man in hydropenia, and assuming medullary osmotic profiles similar to published data on hydropenic dogs, transport coefficients are calculated for each medullary structure. The calculated coefficients compare reasonably well with measurements made in the rat kidney. A normal hydration case is calculated by reducing the collecting duct permeability until a urine output and concentration of 1.0ml/min and 700 mosm/l is obtained. The coefficients are then kept constant, and medullary osmotic profiles and urine output corresponding to various system imputs are calculated. These studies show that medullary osmolarities decrease and urine flow increases with increasing medullary blood flow and that an optimal rate of proximal reabsorption exists for producing a maximally concentrated urine. Such results are consistent with observations on renal function reported both experimentally and clinically.
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PMID:A study of the renal countercurrent system by computer simulation. 47 Nov 43

The renal pelvis of the hamster has been studied by light microscopy (epoxy resin sections), transmission electron microscopy, and morphometric analysis of electron micrographs. Three morphologically distinct epithelia line the pelvis, and each covers a different zone of the kidney. A thin epithelium covering the outer medulla (OM) consists of two cell types: (1) granular cells are most numerous and have apically positioned granules which stain intensely with toluidine blue, are membrane-bound, and contain a fine particulate matter that stains light grey to black in electron micrographs. (2) Basal cells do not have granules, are confined to the basal lamina region, and do not reach the mucosal epithelial surface. The inner medulla (IM) is covered by a pelvic epithelium morphologically similar to collecting duct epithelium of IM. Some cells in this portion of the pelvic epithelium (IM) stain intensely dark with toluidine blue, osmium tetroxide, lead, and uranyl acetate. Transitional epithelium, which separates cortex (C) from pelvic urine, has an asymmetric luminal plasma membrane and discoid vesicles, each of which is similar to those previously observed in mammalian ureter and urinary bladder epithelia. Based on morphological comparisons with other epithelia, the IM and OM pelvic epithelia would appear permeable to solutes and/or water, while the transitional epithelium covering the C appears relatively impermeable. It would also appear that the exchange of solutes and water between pelvic urine and OM would involve capillaries, primarily, since morphometric analysis showed that both fenestrated and continuous capillaries of the OM were extremely abundant (greater than 60% of OM pelvic surface area) just under the thin pelvic epithelium.
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PMID:Ultrastructural organization of the hamster renal pelvis. 48 9


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