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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

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.
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PMID:Segmental heterogeneity of epithelial transport in rat large intestine. 56 27

Using the shrinking droplet method and simultaneous perfusion of the peritubular capillaries the isotonic reabsorption of Ringer's solution from the papillary collecting ducts was measured. Under control conditions the volume reabsorption from the papillary collecting ducts was Jv +/- SE = 2.6 +/- 0.1 . 10(-5) cm3 . cm-2 . s-1. In rats which were on low Na+ diet, Jv increased to 127%, and in adrenalectomized animals it decreased to 34% of the control value. Three hours after a;ocatopm pf a;dpsterpme om tje adrenalectomized animals Jv was partially restored to 63% of control rats. Amiloride 10(-4) M, added to the luminal perfusate, produced a strong inhibition of Jv (to 32% of control). Acetazolamide, 10(-4) M, added to both perfusates, reduced Jv very strongly (to 40% of control), while omission of bicarbonate reduced it only to 77% of control. Acetazolamide, added to bicarbonate-free perfusates, did not result in a significant further reduction of Jv. The data indicate that the Na+ reabsorption from the papillary collecting duct is controlled by mineralocorticoids. Furthermore, they suggest the existence of two transport mechanisms in the luminal cell membrane: 1. An amiloride-sensitive entry step and 2. an entry step via a Na+-H+-countertransport mechanism, the latter being less important.
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PMID:Sodium reabsorption in the papillary collecting duct of rats. Effect of adrenalectomy, low Na+ diet, acetazolamide, HCO-3-free solutions and of amiloride. 57 Nov 3

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

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.
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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 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

In the rabbit kidney, the connecting tubule is a clearly delimited tubular portion interposed between the convoluted part of the distal tubule and the cortical collecting duct. Superficial nephrons have individual connecting tubules; the connecting tubules of deeper nephrons fuse together to form a so-called arcade. The collecting duct is subdivided, with respect to localization, into cortical, outer medullary and inner medullary collecting duct. Connecting tubule and collecting duct are lined by a total of three different cell types: the connecting tubule by the connecting tubule cell and the intercalated cell; the collecting duct by the principal cell and the intercalated cell present only in the cortical and outer medullary segment. The intercalated cell can have different manifestations ("gray", "black", and "light"). The principal cell undergoes gradual alterations from a very complicatedly organized prismatic cell (approximately 7.5 micron cellular height) in the cortical collecting duct to a very simply organized, high prismatic cell (approximately 75 micron cellular height) in the inner medullary collecting duct.
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PMID:Ultrastructural characterization of the connecting tubule and the different segments of the collecting duct system in the rabbit kidney. 61 77

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

A new method combining electron microscopy with microdissection was used to study the segmental variation along the tubule of a marine flounder. Two different nephron types were present. One type had long tubules with the glomeruli located close to the kidney surface. The other type had shorter and more coiled tubules with the glomeruli located close to the terminal end of the same nephron. Five different segments were present: (1) neck segment, (2) first proximal segment, (3) second proximal segment, (4) third proximal segment, and (5) collecting tubule. The third proximal segment was not present in all tubules. An extensive system of infoldings from the plasma membrane was present in all segments, except the neck segment and the collecting tubule. Tight junctions impermeable to lanthanum were present in all segments. The collecting duct cells also had extensive infoldings from the plasma membrane and tight junctions impermeable to lanthanum were also present here.
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PMID:Ultrastructure and segmentation of microdissected kidney tubules in the marine flounder, Pleuronectes platessa. 68 34


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