Activation of Na+-independent Mg2+ efflux by 20-hydroxyeicosatetraenoic acid in rat renal epithelial cells.
Renal epithelial cells may have Mg(2+) transport pathways that regulate intracellular free Mg(2+) concentration ([Mg(2+)](i)) and reabsorption into the body. In mag-fura 2 fluorescent measurement, extracellular Mg(2+) removal induced a Na(+)-independent [Mg(2+)](i) decrease. The [Mg(2+)](i) decrease was suppressed by methyl arachidonyl fluorophosphonate, a cytosolic and Ca(2+)-independent phospholipase A(2) (iPLA(2)) inhibitor, and bromoenol lactone, an iPLA(2) inhibitor, but it was not suppressed by a secretory phospholipase A(2) inhibitor. On the contrary, the [Mg(2+)](i) decrease was enhanced by the addition of exogenous arachidonic acid (AA). Next, we examined the effect of AA metabolite inhibitors on the [Mg(2+)](i) decrease. 17-octadecynoic acid inhibited the [Mg(2+)](i) decrease, but indomethacin and nordihydroguaiaretic acid did not. In the 17-octadecynoic acid-treated cells, 20-hydroxy-(5Z,8Z,11Z,14Z)-eicosatetraenoic acid (20-HETE) recovered the [Mg(2+)](i) decrease. Nicardipine inhibited both the basal and the 20-HETE-enhanced [Mg(2+)](i) decrease. These results suggest that 20-HETE is a key mediator in the activation of Na(+)-independent Mg(2+) efflux.
Ikari
A
A
Department of Environmental Biochemistry and Toxicology, University of Shizuoka School of Pharmaceutical Sciences, Shizuoka 422-8526, Japan. ikari@u-shizuoka-ken.ac.jp
Nakajima
K
K
Suketa
Y
Y
Harada
H
H
Takagi
K
K
D000818:Animals; D004847:Epithelial Cells / Q000502:physiology; D006893:Hydroxyeicosatetraenoic Acids / Q000494:pharmacology*; D007668:Kidney / Q000166:cytology* / Q000502:physiology; D008274:Magnesium / Q000493:pharmacokinetics*; D051381:Rats; D012964:Sodium / Q000494:pharmacology*
D006893:Hydroxyeicosatetraenoic Acids; C055987:20-hydroxy-5,8,11,14-eicosatetraenoic acid; D012964:Sodium; D008274:Magnesium