CYP-omega-hydroxylation-dependent metabolites of arachidonic acid inhibit the basolateral 10 pS chloride channel in the rat thick ascending limb.
Metabolites of arachidonic acid influence sodium chloride (NaCl) transport in the thick ascending limb. Because a 10 pS Cl channel is the major type of chloride channel in the basolateral membrane of this nephron segment, we explored the effect of arachidonic acid on this channel in cell-attached patches. Addition of 5 micromol arachidonic acid significantly decreased channel activity (a product of channel number and open probability) while linoleic acid had no effect. To determine if this was mediated by acachidonic acid per se or by its metabolites, we measured channel activity in the presence of the cyclooxygenase inhibitor indomethacin, the selective lipoxygenase inhibitor nordihydroguaiaretic acid, and the cytochrome P-450 (CYP)-omega-hydroxylation inhibitor 17-octadecynoic acid. Neither cyclooxygenase nor lipoxygenase inhibition had an effect on basal chloride channel activity; further they failed to abolish the inhibitory effect of arachidonate on the 10 pS channel. However, inhibition of CYP-omega-hydroxylation completely abolished the effect of arachidonic acid. The similarity of the effects of 20-hydroxyeicosatetraenoic acid (20-HETE) and arachidonic acid suggests that the effect of arachidonic acid was mediated by CYP-omega-hydroxylation-dependent metabolites. We conclude that arachidonic acid inhibits the 10 pS chloride channel in the basolateral membrane of the medullary thick ascending limb, an effect mediated by the CYP-omega-hydroxylation-dependent metabolite 20-HETE.
Gu
Rui-Min
RM
Department of Pharmacology, Harbin Medical University, China. ruimingu2916@yahoo.com.cn
Yang
Lei
L
Zhang
Yunhong
Y
Wang
Lijun
L
Kong
Shumin
S
Zhang
Chengbiao
C
Zhai
Yuanyuan
Y
Wang
Mingxiao
M
Wu
Peng
P
Liu
Liping
L
Gu
Feng
F
Zhang
Jiye
J
Wang
Wen-Hui
WH
D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism*; D018118:Chloride Channels / Q000037:antagonists & inhibitors* / Q000378:metabolism; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D005260:Female; D006893:Hydroxyeicosatetraenoic Acids / Q000378:metabolism*; D006900:Hydroxylation; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D015640:Ion Channel Gating; D008138:Loop of Henle / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D009637:Masoprocol / Q000494:pharmacology; D008564:Membrane Potentials; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D012965:Sodium Chloride / Q000378:metabolism; D013997:Time Factors
D018118:Chloride Channels; D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors; D005231:Fatty Acids, Unsaturated; D006893:Hydroxyeicosatetraenoic Acids; D016718:Arachidonic Acid; C047008:17-octadecynoic acid; D012965:Sodium Chloride; C055987:20-hydroxy-5,8,11,14-eicosatetraenoic acid; D009637:Masoprocol; D003577:Cytochrome P-450 Enzyme System; C409986:cytochrome P-450 omega-hydroxylase; D007213:Indomethacin