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)

Significant proximal tubular responses to exogenous dopamine require 0.1 to 10 mumol/L concentrations but endogenous peritubular dopamine and DOPA concentrations are in the picomolar to nanomolar range. Dopamine concentration approaches micromolar levels within proximal tubular cells and their brush borders, as a result of DOPA decarboxylation and secretion, and in collecting duct fluid, as a result of tubular fluid absorption. Thus dopamine probably acts either within the proximal tubule cell or brush border or from the collecting tubular lumen. DOPA and Na+ uptake are coupled; dopamine uptake is linked to intracellular electrical potential and its secretion to H+ counter-transport; therefore alterations in proximal tubular Na+ and H+ transport influence dopamine excretion. Haloperidol and SCH 23390 block dopamine excretion, therefore dopamine antagonists may inhibit tubular dopamine responses by lowering intracellular dopamine concentration as well as by receptor blockade. Evidence for an intracellular site of dopamine action can be deduced from the inhibitory effect of DOPA on oxygen consumption and 86Rb uptake in proximal tubule cells. We have confirmed these findings in isolated proximal tubule cells but not in proximal tubule fragments. The discrepant responses may be due to the fact that isolated cells loose their polarity while tubule fragments remain polarized. Dopamine inhibition of proximal tubular Na+, K(+)-ATPase is not reproduced by single dopamine agonists or inhibited by dopamine antagonists. Dopamine effects which are not linked to known dopamine receptors may be the result of redox cycling. Micromolar dopamine oxidizes sulfhydryl groups which may modify enzyme structure and activate protein kinase C.
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PMID:Functional effects of proximal tubular dopamine production. 220 Apr 36

Male MF1-nu/nu/Ola/Hsd nude mice, maintained in a gnotobiotic environment, were dosed i.p. with either 50, 100 or 200 mg/kg 2-bromoethanamine (BEA) hydrobromide to induce a model papillary necrosis. Renal histological changes were examined in semithin glycolmethacrylate resin sections at 24, 48 and 72 h after BEA treatment. The sequence of medullary changes included pyknosis of interstitial cell nuclei, increased staining of the interstitial mucopolysaccharide matrix, platelets adhering to capillary endothelium, necrosis of collecting duct epithelial cells and denudation of the covering epithelium of the papilla. This was similar to that previously described in the Wistar rat, but the time course was extended. There was also a concomitant and extensive cortical necrosis of the P2 and P3 segments of the proximal tubule, which was evident prior to the onset of renal papillary necrosis at the higher doses of BEA. Nude mice show an atypical response to BEA compared to several mouse and rat strains, the hamster and pig, that suggests unique characteristics in this athymic murine mutant.
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PMID:2-Bromoethanamine nephrotoxicity in the nude mouse: an atypical targetting for the renal cortex. 220 87

The localization of two glucose transporter isoforms was mapped in the rat kidney: the high-Michaelis constant (Km; 15-20 mM) low-affinity "liver" transporter and the low-Km (1-2 mM) high-affinity "erythroid/brain" transporter. Both are basolateral membrane proteins, but the liver transporter was present exclusively in the S1 part of the proximal tubule, whereas the erythroid/brain transporter was expressed at variable levels in different nephron segments. Staining intensity was low in the straight proximal tubule (S3), intermediate in the medullary thin and thick ascending limbs, and highest in connecting segments and collecting ducts. In the collecting duct, the erythroid/brain glucose transporter was expressed at the highest level in intercalated cells; less was present in principal cells. In the papilla, only intercalated cells expressed this transporter isoform. These results suggest specific involvements of each transporter isoform in transepithelial glucose reabsorption by different segments of the proximal tubule. They also indicate that while the liver glucose transporter is present in gluconeogenic cells, there is a good correlation between the level of expression of the erythroid/brain glucose transporter and the glycolytic activity of the different nephron segments.
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PMID:Differential localization of two glucose transporter isoforms in rat kidney. 226 Jun 38

Medullary tubules in renal biopsies from twelve patients suffering from ischemic acute tubular necrosis (ATN) and nine patients with allergic, drug-induced acute interstitial nephritis (AIN) were investigated by electron microscopy using quantitative and semiquantitative methods. For comparison, 12 biopsies from patients without renal disease or with minimal change nephropathy were studied. The mean scores for reduction of brush border and basolateral infoldings of the cell surface were significantly increased in the straight part of the proximal tubule and the thick ascending loop of Henle (straight part of the distal tubule) compared with medullary controls, and these changes were significantly greater than the scores for the corresponding convoluted tubules in the cortex. The numbers of missing tubular epithelial cells (indicating sites of cellular desquamation) were significantly increased in the thick ascending loop of Henle in ATN as well as in AIN and in the straight proximal tubule in ATN. This single cell lesion also occurred in the collecting duct. These findings are discussed in the light of recent experimental data indicating the importance of medullary tubules for the pathogenesis of ATN.
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PMID:Ultrastructure of medullary tubules in ischemic acute tubular necrosis and acute interstitial nephritis in man. 228 9

Traditionally, the renal collecting duct has been assigned the dual role of (1) secreting protons derived from dietary metabolism to form luminal NH4+ and titratable acid and (2) generating new HCO3-. This view has recently been challenged. According to current concepts, whole body proton balance is maintained predominantly by the lungs which excrete protons derived from dietary metabolism as the acid anhydride CO2. In the process of excreting CO2, HCO3- is also lost from the body. It is the function of the kidney to generate new HCO3- to replenish this loss. The major site of new HCO3- generation is the proximal tubule rather than the collecting duct. New HCO3- is generated predominantly via the metabolism of organic anions, i.e. alpha-ketoglutarate, citrate, lactate, fatty acids. In the process of generating alpha-ketoglutarate from glutamine, NH4+ is formed. Under normal acid-base conditions, 50% of the NH4+ produced is excreted in the urine, and the remaining 50% is delivered to the renal veins. NH4+ delivered to the renal veins consumes HCO3- during ureagenesis. In the discussion which follows, these new concepts are reviewed and applied to an analysis of the pathophysiology of renal tubular acidosis.
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PMID:The importance of renal ammonia metabolism to whole body acid-base balance: a reanalysis of the pathophysiology of renal tubular acidosis. 228 96

The structure of the nephron in the ranid frog, Rana cancrivora, was studied by light and electron microscopy. This frog is the only amphibian species to live in mangrove swamps of very high salinity. The nephron consists of the following parts: renal corpuscle, ciliated neck segment, proximal tubule, ciliated intermediate segment, distal tubule, connecting tubule, and collecting duct. The distal tubule is located in the ventromedial region of the kidney, and the other tubules are situated in the dorsolateral region. Renal corpuscles are found between the two regions. Some renal corpuscles have a wide Bowman's space because of the small glomerulus within them. The proximal tubules are composed of columnar cells with a dense luminal brush border of long microvilli and numerous apical vesicles and vacuoles. The initial part of the distal tubule consists of heavily interdigitated cells, characterized by a very regular palisade arrangement of mitochondria. In the terminal part of the distal tubule, shorter mitochondria of the infolding cells are situated irregularly around the nucleus. The connecting tubule consists of principal cells and canaliculus cells. The collecting duct consists of columnar or cuboidal cells; cytoplasmic organelles are relatively sparse. The canaliculus cells are intercalated between principal cells from the terminal distal tubule to the proximal part of the collecting duct. Our findings indicate that the kidney of R. cancrivora is structurally similar to kidneys of other amphibians. These findings are discussed with regard to probable correlations between ultrastructure and function in R. cancrivora.
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PMID:Structure of the kidney in the crab-eating frog, Rana cancrivora. 234 60

The sympathetic innervation of the renal tubules and vasculature was characterized by measuring the overlap of accumulations of autoradiographic grains (AAGs) on these structures in autoradiograms of kidney sections from rats injected with tritiated norepinephrine. AAG overlap was used as an indirect measure of the innervation of those structures. The renal vasculature showed x 4.5 more AAG overlap than observed on renal tubules. The greatest amount of AAG overlap occurred on afferent arterioles, followed by efferent arterioles, interlobular arteries, cortical capillaries, arcuate arteries, and renal veins. High concentration of AAGs occurred along the vascular bundles of the outer stripe. In the tubular nephron the proximal tubule had the greatest amount of AAG overlap, followed by the cortical thick ascending limb of Henle, the connecting tubule, the distal convoluted tubule, and the collecting duct. It was found that afferent arterioles had significantly higher mean density of AAG overlap than efferent arterioles for the superficial, midcortical, and juxtamedullary (vascular bundles excluded) renal cortex. There was consistently more AAG perimeter facing the interstitium than overlapping the vasculature. These observations, together with the ultrastructural distribution of synaptic vesicles in varicosities, suggest that the interstitium might be an additional pathway of neurotransmitter access to the effector structures.
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PMID:Monoaminergic innervation of the rat kidney: a quantitative study. 239 76

Na+ entry into kidney epithelial cells occurs by a multiplicity of pathways. Established cell lines such as the A6 cells, derived from the collecting duct of the kidney of Xenopus laevis, MDCK cells, from the distal tubule of a dog kidney, and the LLC-PK1 cells, originating from the proximal tubule of a pig kidney, provide excellent model cell systems for the detailed characterization and isolation of the proteins which comprise these entry pathways. Major pathways of Na+ entry include the amiloride-sensitive Na+ channel, the amiloride-sensitive Na+/H+ antiporter, and the loop diuretic-sensitive NaCl/KCl symporter. While the former two systems have been shown to exhibit an apical location in epithelial cells so far examined, the last system may be localized to either the basolateral or apical surface, depending on the transport function of the cell. Nutrient/Na+ symporters such as the glucose, phosphate, and p-aminohippurate symporters may all be localized to the apical surfaces of proximal tubular cells, but other systems, including those specific for neutral amino acids, may predominate in the basolateral surface or be distributed between the two membranes. Studies concerned with the catalytic, structural, and regulatory properties of these transport systems serve not only to characterize the individual translocators in established cell lines, but also to suggest their physiological functions in intact kidney tissues.
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PMID:Sodium entry pathways in renal epithelial cell lines. 242 Nov 47

Typing of renal cell tumours according to cytomorphological criteria results in different basic cell types, i.e. the clear cell type, the chromophilic cell type, the chromophobic cell type, the oncocytic cell type and the cell type of Duct-Bellini-Carcinoma. Each basic cell type exhibits a typical spectrum of cytological variability including eosinophilic (granular) variants. Antigenic properties of the proximal tubule can mainly be detected in clear cell and chromophilic renal cell carcinomas, whereas antigenic properties of the connecting tubule and collecting duct can be found especially in the chromophobic renal cell carcinoma and oncocytoma as far as in Duct-Bellini-Carcinoma. These different phenotypes of epithelial renal cell tumours are possibly due to various histogenetic pathways. Prognostic factors in renal cell carcinoma include staging, grading and to a less extent cytological and histological parameters which are summarized in a new prognostic score. From this score, three significantly distinct prognostic groups evolved with a correct prognosis of over 80% on the average for an individual case, which suggests a great prognostic potential.
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PMID:[Classification, histogenesis, and prognosis of renal cell carcinoma and renal oncocytoma]. 248 18

We demonstrated the distribution pattern of ecto-5'-nucleotidase (5'-Nu) in rat kidney by enzymatic activity (lead salt precipitation) and by immunohistochemistry with a polyclonal antibody raised in rabbits. Enzyme activity was found in the brush border of the proximal tubule, highest in the P1 segments with decreasing intensity in the P2 segments and weakest in P3 segments in the medullary rays of the cortex. The P3 segments of the outer stripe showed slightly higher activity. Activity was also apparent in the intercalated cells in the connecting tubule and collecting duct, whereas all other tubular and glomerular structures were negative. Activity in peritubular and perivascular connective tissue was highest in the cortical labyrinth, weak or absent in the medullary rays of the cortex, and entirely absent in the medulla. The distribution of the antigen was fully congruent with that of the enzyme activity. With respect to the role of adenosine in regulation of renal blood flow and glomerular filtration rate, the distribution of 5'-Nu in the cortical interstitium may be particularly significant. The possibility of nucleotide cleavage at the brush-border membranes may be important for salvage of nucleotides from the tubular lumen.
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PMID:Ecto-5'-nucleotidase: localization in rat kidney by light microscopic histochemical and immunohistochemical methods. 253 3


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