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)

Insulin-like growth factor I (IGF-I) has been found in the kidney, particularly in the collecting duct in the rat. Since cultured rabbit collecting duct cells constitute a convenient system for in vitro studies, we have examined whether these cells secrete IGF-I. Culture medium conditioned by collecting duct cells was concentrated by reverse phase chromatography and applied to a Sephadex G100 column equilibrated in a denaturing buffer. Two major species with apparent molecular weights of 7.5 and greater than 25 kilodaltons (kD) were identified by IGF-I RIA. A smaller amount of 10 kD species was also observed. Further characterization of 7.5 kD IGF-I immunoreactive species by reverse phase HPLC showed that it eluted in a single peak. To determine whether the higher molecular weight species possessed IGF-I binding activity, appropriate fractions were desalted, incubated with [125I]IGF-I (thr59) for two hours at 30 degrees C and applied to a Sephadex G100 column equilibrated in a non-dissociating buffer. The major peak of radioactivity was confined to a high molecular weight region; there was no radioactivity in the fractions corresponding to 7.5 kD. Western ligand analysis of unreduced conditioned medium identified two IGF-I binding species of 25 and 30 kD, similar in size to species observed in normal rabbit serum. 125I-IGF-I binding as assessed in a charcoal adsorption assay could be displaced by IGF-I and IGF-II but not by insulin. Further characterization of the 10 kD peak of IGF-I immunoreactivity indicated that it did not possess IGF-I binding activity.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Secretion of insulin-like growth factor I and its binding proteins by collecting duct cells. 170

Insulin is known to play an important role in the regulation of extrarenal K homeostasis. Previous clearance studies have shown that insulin decreases urinary K excretion, but the responsible nephron segments have not been identified. In this microperfusion study, in vitro, the effect of insulin on K transport in the cortical collecting duct (CCD), which is thought to be an important segment for regulation of the final urinary K excretion, was investigated. Basolateral insulin (10(-6) M) significantly inhibited net K secretion by 20% (mean JK = -26.2 +/- 4.2 peq.mm-1.min-1 for controls compared with -21.1 +/- 3.4 with insulin, P less than 0.001) and depolarized the transepithelial voltage (VT, from -14.6 +/- 3.5 to -10.8 +/- 3.5 mV, P less than 0.005), recovery did not occur over 60 min. Insulin (10(-11)-10(-5) M) depressed K secretion and depolarized the VT in a concentration-dependent manner. The half-maximal concentration was 5 x 10(-10) M, which is within the physiological range of plasma insulin concentration. In tubules of deoxycorticosterone acetate-treated rabbits, insulin also produced a significant fall in K secretion (from -43.4 +/- 7.5 to -36.1 +/- 5.7 peq.mm-1.min-1, P less than 0.05). Although luminal Ba (2 mM) decreased K secretion (from -14.4 +/- 2.9 to -7.0 +/- 1.7 peq.mm-1.min-1), basolateral insulin (10(-6) M) inhibited K secretion further (to -4.7 +/- 1.3 peq.mm-1.min-1, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effect of insulin on potassium secretion in rabbit cortical collecting ducts. 173 94

Potassium filtered at the glomerulus is almost completely reabsorbed before the distal tubule; it must therefore be secreted into the collecting duct. The rate of potassium secretion is determined by a number of factors, notably aldosterone, distal sodium delivery, and serum potassium. Normal serum potassium is maintained by the interplay of passive leak of potassium from the cells and its active return to the cells. Transmembrane potassium distribution is influenced largely by acid-base equilibrium and hormones including insulin and catecholamines. In the diabetic with ketoacidosis hyperkalemia, in the face of potassium depletion, is attributable to reduced renal function, acidosis, release of potassium from cells due to glycogenolysis, and lack of insulin. Chronic hyperkalemia in diabetics is most often attributable to hyporeninemic hypoaldosteronism but other conditions including urinary tract obstruction may also contribute. A variety of clinical situations (e.g., volume depletion) and drugs (e.g., nonsteroidal antiinflammatory agents, and heparin) may acutely provoke hyperkalemia in susceptible individuals.
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PMID:Hyperkalemia in diabetes mellitus. 183 Mar 19

We have developed an in vitro model of human papillary collecting duct cells isolated from cadaver kidneys using methods similar to those we previously reported for the isolation of human proximal tubule cells. To date we have isolated papillary collecting duct cells from 100 normal human kidneys. Papillae were dissected and digested in Cellgro containing 400 U/ml collagenase. Cells were plated on fibronectin-coated culture flasks at a density of 10(4) live cells/ml in Cellgro supplemented with insulin and 10% fetal bovine serum. Confluent monolayers, which were able to withstand 600 mOSM for 8 h, were obtained within 10 to 15 d. Cells of primary isolates and first passages exhibited epithelial cell ultrastructure including cell junctions, microvilli, and cilia. A dark-brown reaction product was observed in these cells when stained by the immunoperoxidase method with peroxidase-labeled peanut lectin (Arachis hypogaea), which binds specifically to human distal tubule and collecting duct cells. These cells were negative for Factor-VIII (a marker for endothelial cells) and gamma-glutamyltransferase (a marker for proximal tubule cells). High activities of the glycolytic enzyme pyruvate kinase and arginine vasopressin-stimulated cAMP production in these cells are consistent with a distal nephron origin. The results indicate that human collecting duct cells can be isolated and cultured to provide an in vitro system to probe pathogenetic mechanisms of potential nephrotoxins.
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PMID:Characterization of an in vitro system of human renal papillary collecting duct cells. 216 26

Growth hormone (GH) exerts a variety of metabolic and anabolic effects on skeletal and soft tissues including kidney. Some of these actions are mediated directly, whereas others result from GH-dependent synthesis and release of polypeptide growth factors designated insulin-like growth factors (IGFs). Receptors for GH are present in proximal tubule and GH directly stimulates gluconeogenesis at this site. IGF receptors are found in glomerulus and proximal tubule. Mechanisms for signal transduction by GH and IGFs have been characterized using proximal tubular basolateral membranes. IGFs regulate metabolic and transport processes in cultured glomerular mesangial cells and in isolated proximal tubular cells. IGF I is synthesized in cultured mesangial cells and is produced in a GH-dependent manner in cortical and medullary collecting duct. Evidence has accumulated that IGF I of renal origin functions as a paracrine growth factor in the settings of GH-induced hypertrophy and compensatory hypertrophy of the kidney, and in the setting of proximal tubular regeneration following ischemic injury. IGFs are embryonal mitogens and IGF II may act as a transforming agent for Wilms' tumor. Further characterization of the GH-IGF axis in kidney will provide additional insights into the roles of these peptides as regulators of renal function, growth, and development.
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PMID:The growth hormone-insulin-like growth factor axis in kidney. 267 42

Cell culture conditions were devised that selectively supported growth of 13 or 14 gestation day F344 rat ureteric bud, the renal collecting duct anlagen. These same conditions also inhibited the growth of metanephrogenic mesenchyme, precursor of structures proximal to the duct. Isolated buds were cultured in Ham's F12 medium supplemented with epidermal growth factor, selenium, insulin, hydrocortisone, prostaglandin E1, transferrin, and triiodothyronine; fetal bovine serum (1%) was required for continuous propagation. Cultured cells were epithelial in morphology and formed domes. By electron microscopy, many structural characteristics of highly differentiated cells were evident: numerous mitochondria, Golgi apparatus, extensive endoplasmic reticulum, an occasional cilium, intracytoplasmic filaments, polarized formation of microvilli, and gap junctions. Histochemistry revealed considerable functional differentiation as well. Cultured bud cells, adult collecting duct, and fetal duct anlagen were positive for acid phosphatase, membrane-localized ATPase, and nonspecific esterase. Bud cells and fetal duct anlagen expressed high levels of gamma-glutamyl transpeptidase activity while adult collecting duct exhibited slight activity. In addition, immunocytochemical observation of intermediate filament expression revealed the presence of epithelial cytokeratins but absence of mesenchymal vimentin in cultured bud cells and fetal and adult collecting ducts. These results indicate that the culture conditions described can maintain the partially differentiated fetal collecting duct anlagen in a state consistent with its embryonal derivation, and therefore may be useful in culture studies of renal differentiation.
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PMID:Selective growth in culture of fetal rat renal collecting duct anlagen. Morphologic and biochemical characterization. 286 2

We examined the electrophysiological and Na+ transport characteristics of rat papillary collecting duct (PCD) cells grown in primary cultures. Grown as monolayers on polycarbonate filters, the cells displayed similar morphological characteristics to native epithelia. They also bound Dolichus biflorus lectin, a property shared by native cells. Monolayers developed a peak electrical resistance of 100-200 omega.cm2 and a transmonolayer voltage of less than 2 mV. Similar values were measured in the perfused, native PCD of the same species as well as PCD cells cultured from rabbit and bovine kidneys. Hamster cells did not readily develop confluent monolayers under the same conditions. Exposure of the cultured cells to 10% fetal calf serum for 24 h caused the Na+ uptake across the apical membrane to double, an effect not reproduced by indomethacin, insulin, vasopressin, aldosterone, dexamethasone, or hexamethylene bisacetamide (an inducer of differentiation). Amiloride (1 mM) inhibited Na+ uptake by 50-80%. The measured short-circuit current did not correlate with Na+ uptake and was clearly dissociated by exposure to serum. The results suggest that there is more than one mechanism of ion transport by the rat PCD.
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PMID:Characteristics of papillary collecting duct cells in primary culture. 314 84

Free water diuresis in vasopressin-deficient Brattleboro rats does not influence body conservation of chromium (Cr+3), suggesting a proximal tubular site for renal Cr reabsorption. Other data suggest that Cr conservation is accomplished primarily by lack of glomerular filtration or by tissue binding to a specific Cr-binding substance. To provide further data, radiochromium (51Cr) retention and tissue distribution were studied in SHR and WKY rats undergoing saline diuresis. Despite high urine flows, body retention and urinary excretion of 51Cr were unchanged. Tissue content of 51Cr was minimally and not consistently influenced by saline diuresis in either rat strain. Compared to WKY rats, the SHR rats had a trend to lower serum and tissue 51Cr content but higher tissue/serum 51Cr ratios. These data fail to incriminate collecting duct reabsorption in Cr conservation but are compatible with proximal Cr reabsorption or either of the two hypotheses mentioned above. The decreased serum 51Cr content of SHR rats may be due to the mechanical effect of increased plasma and extracellular volumes. One possible explanation for the increased tissue/serum 51Cr ratios may be the presence of a factor in SHR rats promoting cellular Cr transport. However, there is no present evidence to suggest that any of the hormones believed capable of increasing Cr transport (insulin, growth hormone, thyroxine, ADH) are increased in the SHR rat.
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PMID:Radiochromium distribution during saline diuresis. 373 75

Isolated human eccrine sweat glands have been microdissected into their secretory and reabsorptive components. Complete separation of these epithelia was confirmed by differential uptake of Neutral Red stain by an intermediate section of gland containing the junction between the secretory coil and the collecting duct. Primary cultures were obtained from explants of both tissues in medium RPMI-1640 or Williams E supplemented with foetal calf serum, insulin, transferrin, epidermal growth factor and hydrocortisone. The cells in the initial coil cultures had an elongated morphology while those of ductal origin were polyhedral. After 10 days both cultures were composed of polyhedral cells of varying diameter. All these morphological types were of epithelial lineage, as demonstrated by the binding of a monoclonal antibody to cytokeratin, the intermediate filament specific for epithelial cells. Outgrowth from both secretory and reabsorptive epithelia were multilayered, with plentiful desmosomal connections and an underlying basal lamina. Ultrastructural features typical of the epithelial cell types present in intact eccrine sweat glands were absent in a high proportion of the proliferating cells but domes, indicative of transepithelial active ion transport, were present in dense cultures from the reabsorptive duct. Outgrowth was also obtained from the secretory and reabsorptive epithelia of sweat glands from two cystic fibrotic patients. Since the most characteristic malfunction of cystic fibrosis is the impaired ion transport in the eccrine sweat gland, the availability of cultured epithelia should provide a useful model for study of the disease.
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PMID:The primary culture of epithelia from the secretory coil and collecting duct of normal human and cystic fibrotic eccrine sweat glands. 380 34

The aging kidney suffers reduction both in mass and in glomerular filtration rate. These changes may be totally or partially due to atherosclerosis and hypertension, which reduce renal blood flow. Superimposed on these processes, and perhaps responsible for primary loss of renal mass irrespective of renal vascular disease, is glomerular damage and involution that is a consequence of adaptive increases in glomerular perfusion pressure that occurs as the number of nephrons decline with age. The data available at this time do not allow us to distinguish between these two potential mechanisms of renal senescence. The decline in GFR is in turn responsible for reduced renal acidification and the reduced renal clearance of drugs that are normally removed by the kidney. Certain renal functions, however, are depressed to a greater extent than is GFR. Both the ability to maximally dilute the urine and to maximally concentrate it are controlled by serum ADH concentrations and by the action of that hormone on the collecting duct. Aged rats do not maximally secrete ADH under conditions of dehydration and the effect of ADH on the kidney is also attenuated. Elderly humans also cannot maximally suppress ADH secretion when serum osmolality is reduced. Likewise, the renin-angiotensin-aldosterone axis is poorly responsive to volume depletion in aging subjects. As a result, elderly individuals cannot maximally retain sodium under conditions of plasma volume contraction out of proportion to reduction in GFR. The kidney is the site of vitamin D1 hydroxylation. Hydroxylation of vitamin D is reduced out of proportion to any reduction in GFR in the rat. There are no data as yet available on the effect of aging and the production of erythropoietin, a principal regulator of red blood cell mass. Neither are there data available on changes that might occur with advancing age in the ability of the aging kidney to metabolize various hormones, such as parathyroid hormone, glucagon, and insulin. The mechanisms and the full biochemical and physiologic consequences of renal senescence remain to be fully elucidated.
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PMID:The aging kidney. 391


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