scholarly journals Cytochrome P450 metabolites of arachidonic acid are potent inhibitors of vasopressin action on rabbit cortical collecting duct.

1989 ◽  
Vol 84 (6) ◽  
pp. 1805-1812 ◽  
Author(s):  
D L Hirt ◽  
J Capdevila ◽  
J R Falck ◽  
M D Breyer ◽  
H R Jacobson
2004 ◽  
Vol 124 (6) ◽  
pp. 719-727 ◽  
Author(s):  
Yuan Wei ◽  
Dao-Hong Lin ◽  
Rowena Kemp ◽  
Ganesh S.S. Yaddanapudi ◽  
Alberto Nasjletti ◽  
...  

We used the patch-clamp technique to study the effect of arachidonic acid (AA) on epithelial Na channels (ENaC) in the rat cortical collecting duct (CCD). Application of 10 μM AA decreased the ENaC activity defined by NPo from 1.0 to 0.1. The dose–response curve of the AA effect on ENaC shows that 2 μM AA inhibited the ENaC activity by 50%. The effect of AA on ENaC is specific because neither 5,8,11,14-eicosatetraynoic acid (ETYA), a nonmetabolized analogue of AA, nor 11,14,17-eicosatrienoic acid mimicked the inhibitory effect of AA on ENaC. Moreover, inhibition of either cyclooxygenase (COX) with indomethacin or cytochrome P450 (CYP) ω-hydroxylation with N-methylsulfonyl-12,12-dibromododec-11-enamide (DDMS) failed to abolish the effect of AA on ENaC. In contrast, the inhibitory effect of AA on ENaC was absent in the presence of N-methylsulfonyl-6-(propargyloxyphenyl)hexanamide (MS-PPOH), an agent that inhibits CYP-epoxygenase activity. The notion that the inhibitory effect of AA is mediated by CYP-epoxygenase–dependent metabolites is also supported by the observation that application of 200 nM 11,12-epoxyeicosatrienoic acid (EET) inhibited ENaC in the CCD. In contrast, addition of 5,6-, 8,9-, or 14,15-EET failed to decrease ENaC activity. Also, application of 11,12-EET can still reduce ENaC activity in the presence of MS-PPOH, suggesting that 11,12-EET is a mediator for the AA-induced inhibition of ENaC. Furthermore, gas chromatography mass spectrometry analysis detected the presence of 11,12-EET in the CCD and CYP2C23 is expressed in the principal cells of the CCD. We conclude that AA inhibits ENaC activity in the CCD and that the effect of AA is mediated by a CYP-epoxygenase–dependent metabolite, 11,12-EET.


1998 ◽  
Vol 274 (4) ◽  
pp. F728-F735 ◽  
Author(s):  
Mark A. Lal ◽  
Pierre R. Proulx ◽  
Richard L. Hébert

Arachidonic acid (AA) release is the rate-limiting step in the production of prostaglandins, an important class of autocrine/paracrine factors that modulate collecting duct function. Previous results from this laboratory have established cytosolic phospholipase A2(cPLA2) as the enzyme responsible for bradykinin (BK)-stimulated AA mobilization in rabbit cortical collecting duct (RCCD) cells, and the present study pursues the intracellular signaling mechanisms responsible for its activation. Pretreatment of cells with Ro-31-8220, an inhibitor of protein kinase C (PKC), or PD-98059, an inhibitor of the mitogen-activated protein kinase (MAPK) cascade, resulted in a 50–60% reduction in BK-stimulated AA release. Incubation of RCCD cells with a combination of both Ro-31-8220 and PD-98059 did not achieve a greater inhibition of either BK-stimulated AA release or cPLA2 activity, possibly indicating that MAPK activation was dependent upon prior activation of PKC. This was supported by the observation that BK-induced MAPK activation could be reversed by either inhibitor. Additional experiments dealing with immunoblots for PKC isozymes revealed that RCCD cells express PKC species α, γ, ε, and ζ. Following BK stimulation, only PKCε translocated to the particulate fraction. Based on these results, it appears that PKC is activated and involved in the sequential activation of MAPK and cPLA2 following BK treatment. The results also suggest that PKCε may be the isozyme implicated in the process.


1993 ◽  
Vol 265 (3) ◽  
pp. F399-F405 ◽  
Author(s):  
T. Satoh ◽  
H. T. Cohen ◽  
A. I. Katz

We recently reported a novel intracellular mechanism of Na-K-adenosinetriphosphatase (Na-K-ATPase) regulation in the cortical collecting duct (CCD) by agents that increase cell adenosine 3',5'-cyclic monophosphate (cAMP), which involves stimulation of protein kinase A (PKA) and phospholipase A2 (PLA2). We now determined whether this mechanism also operates in other nephron segments. In the medullary thick ascending limb (MTAL) dopamine, the DA1 agonist fenoldopam, forskolin, or dibutyryl-cAMP inhibited Na-K-ATPase activity, similar to results in CCD. In both segments this effect was blocked by 20-residue inhibitory peptide (IP20), a peptide inhibitor of PKA, but not by staurosporine, a protein kinase C (PKC) inhibitor. PKC activators phorbol 12-myristate 13-acetate, phorbol 12,13-dibutyrate, and 1,2-myristate 13-acetate, phorbol 12,13-dibutyrate, and 1,2-dioctanoylglycerol had no effect on Na-K pump activity in either CCD or MTAL. In contrast, all three PKC activators inhibited pump activity in the proximal convoluted tubule (PCT), an effect reproduced only by dopamine or by parathyroid hormone [PTH-(1-34)]. In PCT the pump inhibition by dopamine or PTH-(1-34) was abolished by staurosporine but not by IP20. The PLA2 inhibitor mepacrine prevented the effect of all agents, and arachidonic acid produced a dose-dependent pump inhibition in each of the three segments studied. We conclude that intracellular mechanisms of Na-K-ATPase regulation differ along the nephron, as they involve activation of PKA in CCD and MTAL and of PKC in PCT. These two pathways probably share a common mechanism in stimulating PLA2, arachidonic acid release, and production of eicosanoids in both the proximal and distal nephron.


1996 ◽  
Vol 271 (3) ◽  
pp. F588-F594 ◽  
Author(s):  
C. M. Macica ◽  
Y. Yang ◽  
S. C. Hebert ◽  
W. H. Wang

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.


2008 ◽  
Vol 294 (6) ◽  
pp. F1441-F1447 ◽  
Author(s):  
ZhiJian Wang ◽  
Yuan Wei ◽  
John R. Falck ◽  
Krishnam Raju Atcha ◽  
Wen-Hui Wang

We used the patch-clamp technique to study the effect of arachidonic acid (AA) on basolateral 18-pS K channels in the principal cell of the cortical collecting duct (CCD) of the rat kidney. Application of AA inhibited the 18-pS K channels in a dose-dependent manner and 10 μM AA caused a maximal inhibition. The effect of AA on the 18-pS K channel was specific because application of 11,14,17-eicosatrienoic acid had no effect on channel activity. Also, the inhibitory effect of AA on the 18-pS K channels was abolished by blocking cytochrome P-450 (CYP) epoxygenase with N-methylsulfonyl-6-(propargyloxyphenyl)hexanamide (MS-PPOH) but was not affected by inhibiting CYP ω-hydroxylase or cyclooxygenase. The notion that the inhibitory effect of AA was mediated by CYP epoxygenase-dependent metabolites was further supported by the observation that application of 100 nM 11,12-epoxyeicosatrienoic acid (EET) mimicked the effect of AA and inhibited the basolateral 18-pS K channels. In contrast, addition of either 5,6-, 8,9-, or 14,15-EET failed to inhibit the 18-pS K channels. Moreover, application of 11,12-EET was still able to inhibit the 18-pS K channels in the presence of MS-PPOH. This suggests that 11,12-EET is a mediator for the AA-induced inhibition of the 18-pS K channels. We conclude that AA inhibits basolateral 18-pS K channels by a CYP epoxygenase-dependent pathway and that 11,12-EET is a mediator for the effect of AA on basolateral K channels in the CCD.


1998 ◽  
Vol 274 (1) ◽  
pp. F175-F181 ◽  
Author(s):  
Carolyn M. Macica ◽  
Yinhai Yang ◽  
Kenneth Lerea ◽  
Steven C. Hebert ◽  
Wenhui Wang

We have previously demonstrated that the ROMK channel maintains the property of arachidonic acid (AA) sensitivity observed originally in the native ATP-sensitive K+channel of the rat cortical collecting duct (16). We used the patch-clamp technique to extend these studies to other NH2-terminal splice variants of the ROMK channel family, ROMK2 and ROMK3, expressed in Xenopus oocytes to determine the mechanism by which AA inhibits channel activity. Although the conductance, channel open probability, and open/closed times of the three homologs were determined to be similar, addition of 5–10 μM AA caused only a moderate inhibition of ROMK2 (15 ± 8%) and ROMK3 (13 ± 9%) activity, indicating that differences in the NH2 termini of ROMK channels strongly influence the AA action. We consequently examined the effect of AA on a ROMK1 variant, R1ND37, in which the NH2 terminal amino acids 2–37 were deleted, and on a mutant ROMK1, R1S4A, in which the serine-4 residue was mutated to alanine. Like ROMK2 and ROMK3, AA had a diminished effect on these variants. Addition of 1 nM exogenous protein kinase C (PKC) inhibited ROMK1 but not the mutant, R1S4A. However, the effect of AA is not a result of stimulation of a membrane bound PKC, since PKC inhibitors, calphostin C and chelerythrine, failed to abolish the AA-induced inhibition. In contrast, application of 5 μM staurosporine, a nonspecific protein kinase inhibitor at high concentration, abolished the effect of AA. We conclude that phosphorylation of serine-4 residue in the NH2 terminus plays a key role in determination of AA effect on ROMK channels.


1992 ◽  
Vol 262 (4) ◽  
pp. F554-F559 ◽  
Author(s):  
W. Wang ◽  
A. Cassola ◽  
G. Giebisch

We used the patch-clamp technique to study the effects of arachidonic acid (AA) on the 35-pS secretory K+ channel in the apical membrane of rat cortical collecting duct (CCD). Application of 10 microM AA reversibly reduced channel activity to 1% of the control value [sum of open probability (NPo) decreased from 3.8 to 0.04]. AA inhibits the apical 35-pS K+ channel directly, because application of indomethacin (an inhibitor of cyclooxygenase), nordihydroguaiaretic acid (an enzyme inhibitor of lipoxygenase), and clotrimazole (an inhibitor of epoxygenase) failed to antagonize the AA-induced blocking effect on K+ channel activity. Oleic acid, a cis-unsaturated acid, also blocks K+ channel activity. However, the inhibitory constant (Ki) of oleic acid (5.1 microM) is significantly higher than that of AA (2.6 microM). These results indicate that AA and cis-unsaturated fatty acids are involved in downregulating the apical secretory K+ channel of rat CCD.


2020 ◽  
Vol 152 (8) ◽  
Author(s):  
Morag K. Mansley ◽  
Christian Niklas ◽  
Regina Nacken ◽  
Kathrin Mandery ◽  
Hartmut Glaeser ◽  
...  

Prostaglandin E2 (PGE2) is the most abundant prostanoid in the kidney, affecting a wide range of renal functions. Conflicting data have been reported regarding the effects of PGE2 on tubular water and ion transport. The amiloride-sensitive epithelial sodium channel (ENaC) is rate limiting for transepithelial sodium transport in the aldosterone-sensitive distal nephron. The aim of the present study was to explore a potential role of PGE2 in regulating ENaC in cortical collecting duct (CCD) cells. Short-circuit current (ISC) measurements were performed using the murine mCCDcl1 cell line known to express characteristic properties of CCD principal cells and to be responsive to physiological concentrations of aldosterone and vasopressin. PGE2 stimulated amiloride-sensitive ISC via basolateral prostaglandin E receptors type 4 (EP4) with an EC50 of ∼7.1 nM. The rapid stimulatory effect of PGE2 on ISC resembled that of vasopressin. A maximum response was reached within minutes, coinciding with an increased abundance of β-ENaC at the apical plasma membrane and elevated cytosolic cAMP levels. The effects of PGE2 and vasopressin were nonadditive, indicating similar signaling cascades. Exposing mCCDcl1 cells to aldosterone caused a much slower (∼2 h) increase of the amiloride-sensitive ISC. Interestingly, the rapid effect of PGE2 was preserved even after aldosterone stimulation. Furthermore, application of arachidonic acid also increased the amiloride-sensitive ISC involving basolateral EP4 receptors. Exposure to arachidonic acid resulted in elevated PGE2 in the basolateral medium in a cyclooxygenase 1 (COX-1)–dependent manner. These data suggest that in the cortical collecting duct, locally produced and secreted PGE2 can stimulate ENaC-mediated transepithelial sodium transport.


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