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

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

Recently we described K+ channels in the basolateral membrane of principal cells of rat cortical collecting duct (CCD) which are regulated by a cGMP-dependent protein kinase (Pflugers Arch 429:338-344, 1995). We examined the effects of the NO-liberator sodium nitroprusside (SNP) on single channel activity and membrane voltage (Vm) in principal cells of rat CCD, and on transepithelial voltage, lumen-to-bath Na+ fluxes, and osmotic water permeability in isolated perfused rat CCD tubules. While in patch clamp experiments SNP (10 microM) hyperpolarized principal cells from -54 +/- 10 mV to -71 +/- 5 mV (N = 5) and increased the activity of the described K+ channels from 0.05 +/- 0.03 to 0.45 +/- 0.14 (N = 5) in cell-attached and from 0.04 +/- 0.02 to 0.25 +/- 0.05 (N = 4) in excised patch clamp experiments, it had no effect on basal or AVP-dependent transepithelial voltage, Na+ fluxes, or the osmotic water permeability. In addition, neither 50 microM SIN-1, another liberator of NO, nor 1 mM L-NAME, an inhibitor of the NO-synthase, changed Vm significantly. Furthermore, in cGMP-assays SNP failed to increase intracellular cGMP in CCD segments. Thus, we conclude that in the rat CCD transport is not regulated via the NO-pathway and that SNP acts as an cGMP independent activator of K+ channels in the basolateral membrane of these cells.
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PMID:Effects of sodium nitroprusside in the rat cortical collecting duct are independent of the NO pathway. 902 24

Nitric oxide synthase has been identified in several epithelial cells in the kidney, including proximal tubular cells, thick ascending limb, inner medullary collecting duct, and interstitial cells. Nitric oxide (NO) plays an important role in renal hemodynamics and sodium tubular transport. We have demonstrated that NO participates in hypoxia/reoxygenation (H/R) injury in isolated rat proximal tubules (PT) suspensions. In this in vitro model L-arginine addition enhanced H/R injury while L-NAME almost completely prevented injury. These effects were less intense in chronic supplemented rats with L-arginine and L-NAME, suggesting that NO synthase manipulation had interfered with PT susceptibility to H/R injury. In contrast, L-arginine protected IMCD cells in culture from hypercholesterolemic rats against hypoxia. Moreover, acute infusion of L-arginine before bilateral renal artery clamping was protective while L-arginine chronic administration and L-NAME were deleterious in this ARF model. The L-arginine protection was not observed in unilateral renal clamping plus contralateral nephrectomy in normal rats, but L-arginine was protective in hypercholesterolemic rats. Taken together, these results suggest that the net effect of NO stimulation is variable, and that it is the result of a balance between beneficial hemodynamic effects and cytotoxicity.
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PMID:Role of nitric oxide in acute renal failure. 910 93

We used the patch-clamp technique in the split-open cortical collecting duct (CCD) to investigate the effect of nitric oxide (NO) on the low-conductance (6-pS) Na+ channel that can be blocked by 1 microM amiloride. We confirmed that the number of Na+ channels increased significantly in CCDs of rats on a low-Na+ diet (17). Application of 100 microM N(G)-nitro-L-arginine methyl ester (L-NAME), an agent that blocks endogenous NO synthase, reduced NPo [the product of channel number (N) and open probability (Po)] to 45% of the control value. The effect of L-NAME was specific, since addition of D-NAME, which does not inhibit NO synthase, did not change the activity of the Na+ channel. That the effect of L-NAME results from inhibition of NO synthase is further confirmed by experiments in which addition of an exogenous NO donor, either 10 microM S-nitroso-N-acetyl penicillamine or sodium nitroprusside (SNP), restored the Na+ channel activity when it had been blocked by L-NAME. The action of NO involves a guanosine 3',5'-cyclic monophosphate (cGMP)-dependent pathway, since 100 microM 8-bromo-cGMP (8-BrcGMP) mimicked the effect of SNAP on K+ channels. However, 100 microM 8-BrcGMP did not alter the activity of Na+ channels in inside-out patches, suggesting an indirect action. Because the Na+ channel is activated by hyperpolarization (19) and NO stimulates basolateral K+ channels (16), we tested whether hyperpolarization mediated the effect of NO. In perforated whole cell recordings, addition of L-NAME depolarized the cell membrane from -73 to 51 mV, and application of 10 microM SNP repolarized the membrane to -68 mV. Furthermore, the L-NAME-induced decrease in NPo was effectively restored by 25 mV hyperpolarization of the patch membranes, and addition of 2 mM Ba2+ also abolished the effect of L-NAME. We concluded that the stimulatory effect of NO on the Na+ channel is an indirect effect mediated by a NO-induced increase of basolateral K+ conductance.
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PMID:Nitric oxide-induced hyperpolarization stimulates low-conductance Na+ channel of rat CCD. 914 51

We have used the patch-clamp technique to study the effects of changing extracellular ATP concentration on the activity of the small-conductance potassium channel (SK) on the apical membrane of the mouse cortical collecting duct. In cell-attached patches, the channel conductance and kinetics were similar to its rat homologue. Addition of ATP to the bathing solution of split-open single cortical collecting ducts inhibited SK activity. The inhibition of the channel by ATP was reversible, concentration dependent (K(i) = 64 microM), and could be completely prevented by pretreatment with suramin, a specific purinergic receptor (P(2)) blocker. Ranking of the inhibitory potency of several nucleotides showed strong inhibition by ATP, UTP, and ATP-gamma-S, whereas alpha, beta-Me ATP, and 2-Mes ATP failed to affect channel activity. This nucleotide sensitivity is consistent with P(2)Y(2) purinergic receptors mediating the inhibition of SK by ATP. Single channel analysis further demonstrated that the inhibitory effects of ATP could be elicited through activation of apical receptors. Moreover, the observation that fluoride mimicked the inhibitory action of ATP suggests the activation of G proteins during purinergic receptor stimulation. Channel inhibition by ATP was not affected by blocking phospholipase C and protein kinase C. However, whereas cAMP prevented channel blocking by ATP, blocking protein kinase A failed to abolish the inhibitory effects of ATP. The reduction of K channel activity by ATP could be prevented by okadaic acid, an inhibitor of protein phosphatases, and KT5823, an agent that blocks protein kinase G. Moreover, the effect of ATP was mimicked by cGMP and blocked by L-NAME (N(G)-nitro-l-arginine methyl ester). We conclude that the inhibitory effect of ATP on the apical K channel is mediated by stimulation of P(2)Y(2) receptors and results from increasing dephosphorylation by enhancing PKG-sensitive phosphatase activity.
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PMID:Extracellular ATP inhibits the small-conductance K channel on the apical membrane of the cortical collecting duct from mouse kidney. 1091 72

The present study was designed to investigate the role of nitric oxide (NO) in modulating the adrenergic vasoconstrictor response of the renal medullary circulation. In anesthetized rats, intravenous infusion of norepinephrine (NE) at a subpressor dose of 0.1 microgram. kg(-1). min(-1) did not alter renal cortical (CBF) and medullary (MBF) blood flows measured by laser-Doppler flowmetry nor medullary tissue PO(2) (P(m)O(2)) as measured by a polarographic microelectrode. In the presence of the NO synthase inhibitor nitro-L-arginine methyl ester (L-NAME) in the renal medulla, intravenous infusion of NE significantly reduced MBF by 30% and P(m)O(2) by 37%. With the use of an in vivo microdialysis-oxyhemoglobin NO-trapping technique, we found that intravenous infusion of NE increased interstitial NO concentrations by 43% in the renal medulla. NE-stimulated elevations of tissue NO were completely blocked either by renal medullary interstitial infusion of L-NAME or the alpha(2)-antagonist rauwolscine (30 microgram. kg(-1). min(-1)). Concurrently, intavenous infusion of NE resulted in a significant reduction of MBF in the presence of rauwolscine. The alpha(1)-antagonist prazosin (10 microgram. kg(-1). min(-1) renal medullary interstitial infusion) did not reduce the NE-induced increase in NO production, and NE increased MBF in the presence of prazosin. Microdissection and RT-PCR analyses demonstrated that the vasa recta expressed the mRNA of alpha(2B)-adrenergic receptors and that medullary thick ascending limb and collecting duct expressed the mRNA of both alpha(2A)- and alpha(2B)-adrenergic receptors. These subtypes of alpha(2)-adrenergic receptors may mediate NE-induced NO production in the renal medulla. We conclude that the increase in medullary NO production associated with the activation of alpha(2)-adrenergic receptors counteracts the vasoconstrictor effects of NE in the renal medulla and may play an important role in maintaining a constancy of MBF and medullary oxygenation.
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PMID:alpha(2)-adrenergic receptor-mediated increase in NO production buffers renal medullary vasoconstriction. 1095 33

The effect of L-arginine on transepithelial ion transport was examined in cultured M-1 mouse renal cortical collecting duct (CCD) cells using continuous short circuit current (Isc) measurements in HCO3-/CO2 buffered solution. Steady state Isc averaged 73.8 +/- 3.2 microA/cm2 (n = 126) and was reduced by 94 +/- 0.6% (n = 16) by the apical addition of 100 microM amiloride. This confirms that the predominant electrogenic ion transport in M-1 cells is Na+ absorption via the epithelial sodium channel (ENaC). Experiments using the cationic amino acid L-lysine (radiolabeled) as a stable arginine analogue show that the combined activity of an apical system y+ and a basal amino acid transport system y+L are responsible for most cationic amino acid transport across M-1 cells. Together they generate net absorptive cationic amino acid flux. Application of L-arginine (10 mM) either apically or basolaterally induced a transient peak increase in Isc averaging 36.6 +/- 5.4 microA/cm2 (n = 19) and 32.0 +/- 7.2 microA/cm2 (n = 8), respectively. The response was preserved in the absence of bath Cl- (n = 4), but was abolished either in the absence of apical Na+ (n = 4) or by apical addition of 100 microM amiloride (n = 6). L-lysine, which cannot serve as a precursor of NO, caused a response similar to that of L-arginine (n = 4); neither L-NMMA (100 microM; n = 3) nor L-NAME (1 mM; n = 4) (both NO-synthase inhibitors) affected the Isc response to L-arginine. The effects of arginine or lysine were replicated by alkalinization that mimicked the transient alkalinization of the bath solution upon addition of these amino acids. We conclude that in M-1 cells L-arginine stimulates Na+ absorption via a pH-dependent, but NO-independent mechanism. The observed net cationic amino acid absorption will counteract passive cationic amino acid leak into the CCD in the presence of electrogenic Na+ transport, consistent with reports of stimulated expression of Na+ and cationic amino acid transporters by aldosterone.
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PMID:L-arginine effects on Na+ transport in M-1 mouse cortical collecting duct cells--a cationic amino acid absorbing epithelium. 1131 95

Microelectrode and patch-clamp techniques were used in the isolated cortical collecting duct to study the effects of stimulating Na+-K+-ATPase by raising bath K+ (Fujii Y and Katz AI. Am J Physiol Renal Fluid Electrolyte Physiol 257: F595-F601, 1989 and Muto S, Asano Y, Seldin D, and Giebisch. Am J Physiol Renal Physiol 276: F143-F158, 1999) on the transepithelial (VT) and basolateral membrane (VB) voltages and basolateral K+ channel activity. Increasing bath K+ from 2.5 to 8.5 mM resulted in an initial hyperpolarization of both VT and VB followed by a delayed depolarization. The effects of raising bath K+ on VT and VB were attenuated by decreasing luminal Na+ from 146.8 to 14.0 mM and were abolished by removal of luminal Na+, whereas those were magnified in desoxycorticosterone acetate (DOCA)-treated rabbits. Increasing bath K+ also led to a significant reduction of the intracellular Na+ and Ca2+ concentrations. The transepithelial conductance (GT) or fractional apical membrane resistance (fRA) were unaltered during the initial hyperpolarization phase, whereas, in the late depolarization phase, there were an increase in GT and a decrease in fRA, both of which were attenuated in the presence of low luminal Na+ (14.0 mM). In tubules from DOCA-treated animals, bath Ba2+ not only caused a significantly larger initial hyperpolarization of VT and VB but also blunted the late depolarization by high bath K+. Nomega-nitro-l-arginine methyl ester (l-NAME) partially mimicked the effect of Ba2+ and decreased the amplitude of the late depolarization. Patch-clamp experiments showed that raising bath K+ from 2.5 to 8.5 mM resulted in an increased activity of the basolateral K+ channel, which was absent in the presence of l-NAME. We conclude that stimulation of Na+-K+-ATPase increases the basolateral K+ conductance and that this effect involves suppression of nitric oxide-dependent inhibition of K+ channels.
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PMID:Activity of the basolateral K+ channels is coupled to the Na+-K+-ATPase in the cortical collecting duct. 1453 63

The urea transporters UT-A1 and UT-A3 mediate rapid transepithelial urea transport across the inner medullary collecting duct (IMCD). In a previous study, using a new mouse model in which both UT-A1 and UT-A3 were genetically deleted from the IMCD (UT-A1/3(-/-) mice), we investigated the role of these transporters in the function of the renal inner medulla. Here the authors report a new series of studies investigating more generally the renal phenotype of UT-A1/3(-/-) mice. Pathologic screening of 33 tissues revealed abnormalities in both the testis (increased size) and kidney (decreased size and vascular congestion) of UT-A1/3(-/-) mice. Total urinary nitrate and nitrite (NOx) excretion rates in UT-A1/3(-/-) mice were more than double those in wild-type mice. Total renal blood flow was not different between UT-A1/3(-/-) and wild-type mice but underwent a greater percentage decrease in response to NG-Nitro-L-arginine methyl ester hydrochloride (L-NAME) infusion. Whole kidney GFR (FITC-inulin clearance) was not different in UT-A1/3(-/-) mice compared with controls and underwent a similar increase in response to a greater dietary protein intake. Fractional urea excretion was markedly elevated in UT-A1/3(-/-) mice on a 40% protein diet, reaching 102.4 +/- 8.8% of the filtered load, suggesting that there may be active urea secretion somewhere along the renal tubule. Although there was a marked urinary concentrating defect in UT-A1/3(-/-) mice, there was no decrease in aquaporin 2 or aquaporin 3 expression. Furthermore, although urea accumulation in the inner medulla was markedly attenuated, there was no decrease in sodium ion concentration in tissue from outer medulla or two levels of the inner medulla. These results support our conclusion that the urinary concentrating defect in UT-A1/3(-/-) mice is caused by a failure of urea transport from the IMCD lumen to the inner medullary interstitium, resulting in osmotic diuresis.
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PMID:Renal phenotype of UT-A urea transporter knockout mice. 1582 9

Endothelin-1 (ET-1) inhibition of vasopressin (AVP)-stimulated cAMP accumulation in the collecting duct has been hypothesized to be mediated, at least in part, by nitric oxide (NO). To examine this, the effect of ET-1 on NO production by acutely isolated rat inner medullary collecting duct (IMCD) cell suspensions and the role of NO in mediating ET-1 effects on AVP-stimulated cAMP accumulation were studied. ET-1 dose dependently (first evident at 100 pM ET-1) increased IMCD NO production as determined by DAF-FM fluorescence. ET(B) receptor (BQ-788), but not ET(A) receptor (BQ-123), antagonism blocked this effect. Nonspecific NO synthase (NOS) inhibitors [N(G)-nitro-L-arginine methyl ester (L-NAME) or N(G)-monomethyl-L-arginine] or NOS-1 inhibitors (SMTC or VNIO) inhibited the ET-1 response, whereas NOS-2 or NOS-3 inhibitors (L-NAA or 1400W) were ineffective. ET-1 also increased cGMP accumulation. ET-1 caused a 35% reduction in AVP-stimulated cAMP levels; however, this response was not affected by L-NAME or SMTC. The addition of L-arginine, NADPH, tetrahydrobiopterin, or tempol (to reduce superoxide-dependent conversion of NO to peroxynitrate) did not affect the response. NO donors (SNAP or spermine NONOate), at concentrations that stimulated DAF-FM fluorescence and increased cGMP levels, did not alter AVP-stimulated cAMP accumulation in the IMCD cell suspensions. In conclusion, ET-1 stimulates IMCD NO production through activation of the ET(B) receptor and NOS-1. However, neither ET-1-mediated NO production nor NO donors inhibit AVP-stimulated cAMP accumulation, indicating that NO does not mediate ET-1 inhibition of cAMP production by the IMCD.
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PMID:Endothelin-1 stimulates NO production and inhibits cAMP accumulation in rat inner medullary collecting duct through independent pathways. 1638 Apr 57


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