scholarly journals Arachidonic Acid Inhibits Epithelial Na Channel Via Cytochrome P450 (CYP) Epoxygenase-dependent Metabolic Pathways

2004 ◽  
Vol 124 (6) ◽  
pp. 719-727 ◽  
Author(s):  
Yuan Wei ◽  
Dao-Hong Lin ◽  
Rowena Kemp ◽  
Ganesh S.S. Yaddanapudi ◽  
Alberto Nasjletti ◽  
...  
Keyword(s):  
Arachidonic Acid ◽  
Cytochrome P450 ◽  
Collecting Duct ◽  
Inhibitory Effect ◽  
Mass Spectrometry Analysis ◽  
Gas Chromatography Mass Spectrometry ◽  
Na Channel ◽  
Cortical Collecting Duct ◽  
Patch Clamp Technique ◽  
Spectrometry Analysis

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.

scholarly journals Arachidonic acid inhibits basolateral K channels in the cortical collecting duct via cytochrome P-450 epoxygenase-dependent metabolic pathways

2008 ◽  
Vol 294 (6) ◽  
pp. F1441-F1447 ◽  
Author(s):  
ZhiJian Wang ◽  
Yuan Wei ◽  
John R. Falck ◽  
Krishnam Raju Atcha ◽  
Wen-Hui Wang
Keyword(s):  
Arachidonic Acid ◽  
Collecting Duct ◽  
Rat Kidney ◽  
Inhibitory Effect ◽  
K Channel ◽  
Dependent Manner ◽  
Cortical Collecting Duct ◽  
Patch Clamp Technique ◽  
K Channels ◽  
Cytochrome P 450

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.

scholarly journals Phytochemistry, gas chromatography-mass spectrometry analysis and in vitro anti-bacterial activities of Desplatsia dewevrei (De Wild. & T. Durand)

2018 ◽  
Vol 5 (10) ◽  
pp. 373-404
Author(s):  
Oghale Ovuakporie-Uvo ◽  
MacDonald Idu ◽  
Anne O. Itemire
Keyword(s):  
Inhibitory Effect ◽  
Mass Spectrometry Analysis ◽  
Gas Chromatography Mass Spectrometry ◽  
Useful Plants ◽  
Zone Of Inhibition ◽  
Spectrometry Analysis ◽  
Gram Positive Bacteria ◽  
Quantitative Analyses ◽  
Bacterial Effect

Phytochemicals have been reported to have direct and/or indirect influence on the antibacterial potentials of useful plants. The present study was aimed at determining the phyto-components by traditional methods and GC-MS analysis alongside testing the anti-bacterial activities of Desplatsia dewevrei leaves and fruits. The maceration of 500 g of Desplatsia dewevrei powder in methanol yielded 5.7 g of extract. Qualitatively coumarins were found to be richly present in the leaves while, quinones were most evidently present in the fruits of Desplatsia dewevrei. Quantitative analyses show that the phenolic and tannic acid contents of Desplatsia dewevrei may be the chief compounds responsible for the antibacterial activity of the plant. GC-MS results of Desplatsia dewevrei fruits and leaves respectively showed Gas Chromatograms having 33 and 63 peaks representing different phyto-compounds. Of the 33 and 63 phyto-compounds, Cyclohexanepropanol, alpha.,2,2,6-tetrame-thyl and Farnesyl bromide were recurrent at different retention time. Although Desplatsia dewevrei showed no zone of inhibition for gram negative bacteria, its inhibitory effect on gram positive bacteria is significant. In conclusion, D. dewevrei is a phytochemical rich plant. However, a further study on the anti-bacterial effect of Desplatsia dewevrei using solvent extracts other than methanol is recommended for future incorporation in drug development.

Incorporation of arachidonic acid into lipids of the isolated perfused rat lung

1989 ◽  
Vol 66 (6) ◽  
pp. 2763-2771 ◽  
Author(s):  
F. H. Chilton ◽  
J. Y. Westcott ◽  
L. M. Zapp ◽  
J. E. Henson ◽  
N. F. Voelkel
Keyword(s):  
Arachidonic Acid ◽  
Molecular Species ◽  
Mass Spectrometry Analysis ◽  
Gas Chromatography Mass Spectrometry ◽  
Alveolar Type ◽  
Rat Lung ◽  
Spectrometry Analysis ◽  
Autoradiographic Analysis ◽  
Isolated Rat Lung ◽  
Stimulation Of

This study has attempted to identify the cells and phosphoglyceride molecular species associated with the rapid turnover of arachidonic acid (AA) in the isolated rat lung. In initial studies, AA complexed to trace amounts of albumin was added to the perfusate of rat lungs for 15 min and the incorporation of [3H]AA into various cells and phosphoglyceride molecular species was determined. Autoradiographic analysis revealed that the AA had labeled endothelial cells but also had already escaped from the intravascular space and labeled epithelial cells including alveolar type II cells. In addition, [3H]AA was found to be incorporated into various phosphoglycerides: phosphatidylcholine (PC) greater than phosphatidylethanolamine (PE) greater than phosphatidylinositol (PI). The majority of this [3H]AA was incorporated into 1-acyl-2-arachidonoyl-sn-glycero-3-PC, -PE, and -PI during the 15-min labeling period. In subsequent experiments, AA remodeling in the lung was examined by pulse labeling with [3H]AA for 15 min, washing unbound AA with albumin, and perfusing for an additional 120 min. In these lungs, some of the [3H]AA was remodeled into 1-alk-1-enyl-acyl-sn-glycero-3-PE. Gas chromatography-mass spectrometry analysis revealed that the largest pools of endogenous AA in the lung are found in PE associated with 1-alk-1-enyl-linked molecular species. On ionophore stimulation of lungs labeled for 15 min, labeled leukotriene (LT) B4, leukotriene C4, and 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha) were produced. LTC4 had a profoundly different radiospecific activity compared with LTB4 and 6-keto-PGF1 alpha, suggesting a different source of AA as contributing to the production of this eicosanoid.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Role of the NH2 terminus of the cloned renal K+ channel, ROMK1, in arachidonic acid-mediated inhibition

1998 ◽  
Vol 274 (1) ◽  
pp. F175-F181 ◽  
Author(s):  
Carolyn M. Macica ◽  
Yinhai Yang ◽  
Kenneth Lerea ◽  
Steven C. Hebert ◽  
Wenhui Wang
Keyword(s):  
Arachidonic Acid ◽  
Protein Kinase ◽  
Kinase Inhibitor ◽  
Splice Variants ◽  
Collecting Duct ◽  
K Channel ◽  
Cortical Collecting Duct ◽  
High Concentration ◽  
Patch Clamp Technique ◽  
Open Probability

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.

Reaction of nitric oxide with superoxide inhibits basolateral K+ channels in the rat CCD

1998 ◽  
Vol 275 (1) ◽  
pp. C309-C316 ◽  
Author(s):  
Ming Lu ◽  
Wen-Hui Wang
Keyword(s):  
Nitric Oxide ◽  
Collecting Duct ◽  
Rat Kidney ◽  
Inhibitory Effect ◽  
Cortical Collecting Duct ◽  
Channel Activity ◽  
High Concentration ◽  
Patch Clamp Technique ◽  
Open Probability ◽  
No Donors

We previously demonstrated that nitric oxide (NO) stimulates the basolateral small-conductance K+channel (SK) via a cGMP-dependent pathway [M. Lu and W. H. Wang. Am. J. Physiol. 270 ( Cell Physiol. 39): C1336–C1342, 1996]. Because NO at high concentration has been shown to react with superoxide ([Formula: see text]) to form peroxynitrite (OONO−) [W. A. Pryor and G. L. Squadrito. Am. J. Physiol. 268 ( Lung Cell. Mol. Physiol. 12): L699–L722, 1995 and M. S. Wolin. Microcirculation 3: 1–17, 1996], we extended our study to examine, using patch-clamp technique, the effect of high concentrations of NO on SK in cortical collecting duct (CCD) of rat kidney. Addition of NO donors [100–200 μM S-nitroso- N-acetyl-penicillamine (SNAP) or sodium nitroprusside (SNP)] reduced channel activity, defined as the product of channel number and open probability, to 15 and 25% of the control value, respectively. The inhibitory effect of NO was completely abolished in the presence of 10 mM Tiron, an intracellular scavenger of [Formula: see text]. NO donors, 10 μM SNAP or SNP, which stimulate channel activity under control conditions, can also inhibit SK in the presence of an[Formula: see text] donor, pyrogallol, or in the presence of an inhibitor of superoxide dismutase, diethyldithiocarbamic acid. The inhibitory effect of NO is still observed in the presence of exogenous cGMP, suggesting that the NO-induced inhibition is not the result of decreased cGMP production. We conclude that the inhibitory effect of NO on channel activity results from an interaction between NO and [Formula: see text].

Arachidonic acid inhibits the secretory K+ channel of cortical collecting duct of rat kidney

1992 ◽  
Vol 262 (4) ◽  
pp. F554-F559 ◽  
Author(s):  
W. Wang ◽  
A. Cassola ◽  
G. Giebisch
Keyword(s):  
Arachidonic Acid ◽  
Oleic Acid ◽  
Unsaturated Fatty Acids ◽  
Enzyme Inhibitor ◽  
Collecting Duct ◽  
K Channel ◽  
Cortical Collecting Duct ◽  
Channel Activity ◽  
Patch Clamp Technique ◽  
Open Probability

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.

Nitric oxide regulates the low-conductance K+ channel in basolateral membrane of cortical collecting duct

1996 ◽  
Vol 270 (5) ◽  
pp. C1336-C1342 ◽  
Author(s):  
M. Lu ◽  
W. H. Wang
Keyword(s):  
Nitric Oxide ◽  
Collecting Duct ◽  
Rat Kidney ◽  
Basolateral Membrane ◽  
Inhibitory Effect ◽  
K Channel ◽  
Cortical Collecting Duct ◽  
Channel Activity ◽  
Patch Clamp Technique ◽  
Dependent Pathway

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.

Nitric oxide-induced hyperpolarization stimulates low-conductance Na+ channel of rat CCD

1997 ◽  
Vol 272 (4) ◽  
pp. F498-F504 ◽  
Author(s):  
M. Lu ◽  
G. Giebisch ◽  
W. Wang
Keyword(s):  
Nitric Oxide ◽  
Collecting Duct ◽  
No Synthase ◽  
Na Channel ◽  
Na Channels ◽  
Cortical Collecting Duct ◽  
Patch Clamp Technique ◽  
Open Probability ◽  
No Donor ◽  
K Channels

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.

Sign in / Sign up

Export Citation Format

Share Document