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)

Preservation of cell viability and function in the hyperosmolar environment of the renal medulla is a complex process that requires selective gene expression. We have identified a new member of the heat shock protein (hsp) 70 superfamily that is up-regulated in renal inner medullary collecting duct cells (mIMCD3 cells) during exposure to hyperosmotic NaCl stress. Known as osmotic stress protein 94, or Osp94, this 2935-base pair cDNA encodes an 838-amino acid protein that shows greatest homology to the recently discovered hsp110/SSE gene subfamily. Like the hsps, Osp94 has a putative amino-terminal ATP-binding domain and a putative carboxyl-terminal peptide-binding domain. The in vitro translated Osp94 product migrated as a 105-110-kDa protein on SDS-polyacrylamide gel electrophoresis. In mIMCD3 cells, Osp94 mRNA expression was greatly up-regulated by hyperosmotic NaCl or heat stress. In mouse kidney, Osp94 mRNA expression paralleled the known corticomedullary osmolality gradient showing highest expression in the inner medulla. Moreover, inner medullary Osp94 expression was increased during water restriction when osmolality is known to increase. Thus, Osp94 is a new member of the hsp110/SSE stress protein subfamily and likely acts as a molecular chaperone.
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PMID:Osmotic stress protein 94 (Osp94). A new member of the Hsp110/SSE gene subfamily. 864 34

Rabbit connecting tubule and cortical collecting duct cells were isolated by immunodissection and cultured to confluence on permeable filters and on glass coverslips. Extracellular ATP dose-dependently reduced transcellular Na+ and Ca2+ transport (half-maximal inhibitory concentration, IC50, of 0.5 +/- 0.2 and 3.2 +/- 0.5 microM), with a maximal inhibition of 57 +/- 5 and 43 +/- 4%, respectively. Purinergic receptor agonists inhibited transport with the following rank order of potency: UTP = ATP > ADP; this suggests involvement of P2u purinoceptors. ATP also caused a dose-dependent (50% effective dose, EC50, of 1.5 +/- 0.2 microM) transient increase in intracellular Ca2+ concentration ([Ca2+]i), which decreased to a sustained elevated level. In the absence of extracellular Ca2+, a similar Ca2+ transient occurred, but the sustained response was abolished. Preloading the cells with the Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) completely prevented the ATP-induced Ca2+ transients, but not the ATP-induced inhibition of Na+ and Ca2+ absorption. Activation of protein kinase C (PKC) by the cell-permeable diacylglycerol analogue, 1,2-dioctanoyl-en-glycerol, mimicked ATP-induced inhibition of Na+ and Ca2+ absorption. The inhibitory effects of ATP were no longer observed after culturing cells in the presence of phorbol ester (12-O-tetradecanoylphorbol-13-acetate) for 5 days, which resulted in downregulation of cellular PKC activity.
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PMID:Inhibition of Na+ and Ca2+ reabsorption by P2u purinoceptors requires PKC but not Ca2+ signaling. 876 22

We established renal cell lines from definite nephron segments which were microdissected from kidneys of transgenic C57BL/6 mice, harboring the large T-antigen gene of temperature-sensitive mutant simian virus 40, pSVtsA58(ori-). Cell culture was under a humidified atmosphere of 5% CO2 in air, on collagen-coated dishes, and in RITC80-7 medium with 5% fetal bovine serum, 10 micrograms/ml transferrin, 1 microgram/ml insulin, 10 ng/ml recombinant human EGF, penicillin and streptomycin. Cell line which kept contact inhibition character was established from each segment. Cells derived from distal tubule, cortical and outer medullary collecting duct possessed their cyclic AMP response to arginine-vasopressin, like their original nephron segment. On the other hand, cells derived from terminal proximal tubules (S3 segment) formed a cobblestone-like confluent monolayer, and did not respond to arginine-vasopressin like their fresh segments. Since cisplatin, a well-known nephrotoxic substance, damages proximal tubules (especially S3) rather than collecting ducts, we assayed cell number, protein content, and ATP content of cultured S3 cells at various times after addition of 0.2 mM cisplatin. Decrease of cell number, total protein content and total ATP content of culture cells occurred after 10 h incubation with 0.2 mM cisplatin. The 50% lethal dose (LD50) of cisplatin in S3 cells was 4 x 10(-5) M after 20 h incubation and 8.5 x 10(-6) M after 40 h incubation. Outer medullary collecting duct (OMCD) cells were damaged 30% maximally after 20 h incubation with cisplatin, and LD50 in them became 2.5 x 10(-5) M after 40 h incubation. We could show that the LD50 of cisplatin in the OMCD cell line was three times higher than that in the S3 cell line. Thus, these cell lines are the first in the kidney to definite the segmental origin and to maintain some differentiated unique functions. They are valuable for studies on intrarenal site-specific actions and possible mechanisms of action of pharmacological and toxic substances.
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PMID:Cisplatin-induced toxicity in immortalized renal cell lines established from transgenic mice harboring temperature sensitive SV40 large T-antigen gene. 885 99

The hypertonic environment of the renal medulla can change rapidly according to the state of hydration of the animal. We used primary cultures of rat inner medullary collecting duct (IMCD) cells to investigate the characteristics of Cl- currents activated by an acute reduction in osmolarity (ICl(osm)). Using the whole cell patch-clamp technique, we identified an outwardly rectifying current that decayed slowly at strongly depolarizing voltages. The onset of ICl(osm) began 6.7 min after the fall in bath osmolarity, a delay longer than reported in other cell types. Hypotonicity did not induce an increase in intracellular Ca2+ concentration, and activation of ICl(osm) did not require the presence of Ca2+. Intracellular ATP was needed to evoke ICl(osm) when the hypotonic stimulus was modest (50 mosmol/l or less) but was not necessary when the stimulus was stronger (100 mosmol/ l). ICl(osm) was inhibited by 5-nitro-2-(3-phenylpropylamino)benzoic acid but not by tamoxifen or glibenclamide. 4,4'-Diisothiocyanostilbene-2,2'-disulfonic acid produced a voltage-dependent block. Acute reduction in osmolarity using cells grown on filters did not induce a Cl- secretory current. The ICl(osm) of IMCD cells appears to be on the basolateral membrane and displays some unique features.
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PMID:Cl- current in IMCD cells activated by hypotonicity: time course, ATP dependence, and inhibitors. 885 16

Arachidonic acid (AA) has been shown to inhibit the activity of the low-conductance ATP-sensitive K+ channel in the apical membrane of the cortical collecting duct [W. Wang, A. Cassola, and G. Giebisch. Am. J. Physiol. 262 (Renal Fluid Electrolyte Physiol. 31): F554-F559, 1992]. ROMK1, a K+ channel derived from the rat renal outer medulla, shares many biophysical properties of the native low-conductance K+ channel, which is localized to the apical membranes of the cortical collecting duct and thick ascending limb. This study was designed to determine whether the ROMK channel maintains the property of AA sensitivity of the native low-conductance K+ channel. Experiments were conducted in Xenopus oocytes injected with cRNA encoding the ROMK1 channel by use of patch-clamp techniques. We have confirmed previous reports that the cloned ROMK1 has similar channel kinetics, high open probability, and inward slope conductance as the native low-conductance K+ channel, respectively. Addition of 5 microM AA to an inside-out patch resulted in reversible inhibition of channel activity at a concentration similar to the inhibitor constant for AA on the native K+ channel. The effect of AA on channel activity was preserved in the presence of 10 microM indomethacin, a cyclooxygenase inhibitor, 4 microM cinnamyl-3,4-dihydroxycyanocinnamate, a lipoxygenase inhibitor, and 4 microM 17-octadecynoic acid, an inhibitor of cytochrome P-450 monooxygenases, thus indicating that the effect of AA was not mediated by metabolites of AA. The effect did not appear to be the result of changes in membrane fluidity, since 5 microM eicosatetraynoic acid, an AA analogue that is a potent modulator of membrane fluidity, had no effect. Furthermore, the addition of AA to the outside of the patch also had no effect on channel activity. These results indicate that, like the native low-conductance channel, AA is able to directly inhibit ROMK1 channel activity.
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PMID:Arachidonic acid inhibits activity of cloned renal K+ channel, ROMK1. 885 20

ATP-sensitive K+ channels (KATP channels) form a link between the metabolic state of the cell and the permeability of the cell membrane for K+ which, in turn, is a major determinant of cell membrane potential. KATP channels are found in many different cell types. Their regulation by ATP and other nucleotides and their modulation by other cellular factors such as pH and kinase activity varies widely and is fine-tuned for the function that these channels have to fulfill. In most excitable tissues they are closed and open when cell metabolism is impaired; thereby the cell is clamped in the resting state which saves ATP and helps to preserve the structural integrity of the cell. There are, however, notable exceptions from this rule; in pancreatic beta-cells, certain neurons and some vascular beds, these channels are open during the normal functioning of the cell. In the renal tubular system, KATP channels are found in the proximal tubule, the thick ascending limb of Henle's loop and the cortical collecting duct. Under physiological conditions, these channels have a high open probability and play an important role in the reabsorption of electrolytes and solutes as well as in K+ homeostasis. The physiological role of their nucleotide sensitivity is not entirely clear; one consequence is the coupling of channel activity to the activity of the Na-K-ATPase (pump-leak coupling), resulting in coordinated vectorial transport. In ischemia, however, the reduced ATP/ADP ratio would increase the open probability of the KATP channels independently from pump activity; this is particularly dangerous in the proximal tubule, where 60 to 70% of the glomerular ultrafiltrate is reabsorbed. The pharmacology of KATP channels is well developed including the sulphonylureas as standard blockers and the structurally heterogeneous family of channel openers. Blockers and openers, exemplified by glibenclamide and levcromakalim, show a wide spectrum of affinities towards the different types of KATP channels. Recent cloning efforts have solved the mystery about the structure of the channel: the KATP channels in the pancreatic beta-cell and in the principal cell of the renal cortical collecting duct are heteromultimers, composed of an inwardly rectifying K+ channel and sulphonylurea binding subunit(s) with unknown stoichiometry. The proteins making up the KATP channel in these two cell types are different (though homologous), explaining the physiological and pharmacological differences between these channel subtypes.
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PMID:ATP-sensitive K+ channels in the kidney. 887 50

In the present study we used whole-cell patch clamp recordings to investigate swelling-activated Cl-currents (ICl-swell) in M-1 mouse cortical collecting duct (CCD) cells. Hypotonic cell swelling reversibly increased the whole-cell Cl- conductance by about 30-fold. The I-V relationship was outwardly-rectifying and ICl-swell displayed a characteristic voltage-dependence with relatively fast inactivation upon large depolarizing and slow activation upon hyperpolarizing voltage steps. Reversal potential measurements revealed a selectivity sequence SCN- > I- > Br- > Cl- > > gluconate. ICl-swell was inhibited by tamoxifen, NPPB (5-nitro-2(3-phenylpropylamino)-benzoate), DIDS (4,4'-diisothiocyanostilbene-2,2'-disulphonic acid), flufenamic acid, niflumic acid, and glibenclamide, in descending order of potency. Extracellular cAMP had no significant effect. ICl-swell was Ca2+ independent, but current activation depended on the presence of a high-energy gamma-phosphate group from intracellular ATP or ATP gamma S. Moreover, it depended on the presence of intracellular Mg2+ and was inhibited by staurosporine, which indicates that a phosphorylation step is involved in channel activation. Increasing the cytosolic Ca2+ concentration by using ionomycin stimulated Cl- currents with a voltage dependence different from that of ICl-swell. Analysis of whole-cell current records during early onset of ICl-swell and during final recovery revealed discontinuous step-like changes of the whole-cell current level which were not observed under nonswelling conditions. A single-channel I-V curve constructed using the smallest resolvable current transitions detected at various holding potentials and revealed a slope conductance of 55, 15, and 8 pS at +120, 0, and -120 mV, respectively. The larger current steps observed in these recordings had about 2, 3, or 4 times the size of the putative single-channel current amplitude, suggesting a coordinated gating of several individual channels or channel subunits. In conclusion we have functionally characterized ICl-swell in M-1 CCD cells and have identified the underlying single channels in whole-cell current recordings.
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PMID:Cell swelling activates ATP-dependent voltage-gated chloride channels in M-1 mouse cortical collecting duct cells. 888 62

The M-1 cell line is derived from the mouse cortical collecting duct and displays the low-conductance, highly Na(+)-selective channel activity of the alpha,beta, gamma-heterotrimeric epithelial Na+ channel (ENaC). The short-circuit current (Isc) across M-1 monolayers was 89 +/- 4 microA/cm2, and the transepithelial conductance was 2.1 +/- 0.2 mS/cm2. Isc was abolished by blocking the Na+ pump with ouabain. Both Isc and transepithelial conductance (gT) were inhibited by benzamil > amiloride >> dimethylamiloride. Under our experimental conditions, vasopressin, vasopressin, forskolin, and dibutyryl adenosine 3',5'-cyclic monophosphate (cAMP) had no detectable effects on Isc or gT. Increasing apical Na+ entry with nystatin increased Isc. The possible regulation of the M-1 Na+ channel by cAMP-activated protein kinase A (PKA) was further examined with excised inside-out patches. The open-time probability (Po) was not fixed, displaying substantial variance. Perfusion with ATP itself, with the catalytic subunit of PKA with ATP, or with alkaline phosphatase had no consistent effect on Po, the unitary current, or the kinetics of the M-1 Na+ channel. The data are consistent with the concept that PKA stimulates ENaCs by phosphorylating a site with access to but not within the apical membrane patch during cell-attached and excised-patch studies.
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PMID:Regulation of epithelial Na+ channels from M-1 cortical collecting duct cells. 889 16

Dahl salt-sensitive (S) rats develop hypertension in response to a high-salt diet, whereas Dahl salt-resistant (R) rats do not. There is good evidence that the Dahl S kidneys have diminished natriuretic capacity. We studied the rate of Na+ transport by primary cultures of the inner medullary collecting duct from these two strains to determine whether there were intrinsic differences. Monolayers obtained from prehypertensive S rats transported Na+ at twice the rate as monolayers from age-matched R rats. Mineralocorticoid and glucocorticoid hormones increased Na+ transport from both strains; the S rat monolayers always displayed higher transport rates than R rat monolayers with the same treatment. The Na+ entry pathway in both S and R rat monolayers was via an Na+ channel. The difference in Na+ transport was not explained by a difference in the metabolism of corticosterone, ATP content, citrate synthase activity, ultrastructural appearance, or rate of maturation. Monolayers from S rats tended to have higher protein and DNA content, but these differences could not account for the difference in Na+ transport. Anion secretion in response to adenosine 3',5'-cyclic monophosphate agonists was similar. These results demonstrate intrinsic differences in renal tubular cells that may play an important role in the pathogenesis of salt-sensitive hypertension.
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PMID:IMCD cells cultured from Dahl S rats absorb more Na+ than Dahl R rats. 894 97

Two types of K+ channels, low conductance (28 pS) and intermediate conductance (85 pS), have been previously identified in the basolateral membrane of the cortical collecting duct (CCD) of the rat kidney (31, 32). In the present study, we used the patch-clamp technique to explore further the mechanism by which the low-conductance K+ channel is regulated. The conductance of the low-conductance K+ channel is inward rectifying, with an inward slope conductance of 30 pS between 0 and -20 mV and an outward slope conductance of 16 pS between 0 and 50 mV in symmetrical 140 mM KCl in the bath and in the pipette. This K+ channel was not sensitive to ATP (10 mM), tetraethylammonium chloride (5 mM), and quinidine (1 mM). Addition of 100 microM N omega-nitro-L-arginine methyl ester (L-NAME) or N omega-(imonoethyl)-L-ornithine (L-NIO), an inhibitor of nitric oxide synthase (NOS), completely blocked channel activity in cell-attached patches. In contrast, addition of 200 microM-D-NAME, which does not block NOS, had no effect on channel activity. The inhibitory effect of L-NAME or L-NIO was fully reversible and completely overcome by addition of exogenous nitric oxide (NO) donors, such as 10 microM S-nitroso-N-acetyl-penicillamine or sodium nitroprusside. Furthermore, addition of 100 microM 8-bromoguanosine 3',5'-cyclic monophosphate (8-BrcGMP) restored the activity of the channel when it had been inhibited by either L-NAME or L-NIO, indicating that the effect of NO on the channel activity was mediated by a cGMP-dependent pathway. In conclusion, NO plays a key role in the regulation of the basolateral 30-pS K+ channel and the effect of NO on channel activity is mediated by a cGMP-dependent pathway.
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PMID:Nitric oxide regulates the low-conductance K+ channel in basolateral membrane of cortical collecting duct. 896 33


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