20-HYDROXYEICOSA-TETRAENOIC ACID (20-HETE) ACTIVATES PROTEIN-KINASE-C- ROLE IN REGULATION OF RAT RENAL NA-ATPASE(,K+)

It is well documented that the activity of Na+,K+-ATPase can be inhibi ted by the arachidonic acid metabolite, 20-hydroxyeicosa-tetraenoic ac id (20 HETE). Evidence is presented here that this effect is mediated by protein kinase C (PKC). PKC inhibitors abolished 20 HETE inhibition of rat Na+,K+-ATPase in renal tubular cells. 20 HETE caused transloca tion of PKC alpha from cytoplasm to membrane in COS cells. It also inh ibited Na+,K+-ATPase activity in COS cells transfected with rat wild-t ype renal Na+,K+-ATPase alpha(1) subunit, but not in cells transfected with Na+,K+-ATPase alpha 1, where the PKC phosphorylation site, serin e 23, had been mutated to alanine. PKC-induced phosphorylation of rat renal Na+,K+-ATPase, as well as of histone was strongly enhanced by 20 HETE at the physiologic calcium concentration of 1.3 mu M, but not at the calcium concentration of 200 mu>M. The results indicate that phos pholipase A(2)-arachidonic acid-20 HETE pathway can exert important bi ological effects via activation of PKC and that this effect may occur in the absence of a rise in intracellular calcium.