Modulation of Na, K-ATPase activity by prostaglandin E 1 and [ d-Ala 2, N-Me-Phe 4,Gly 5-ol]-enkephalin

Abstract

Adenylyl cyclase is activated by prostaglandin E and inhibited by mu-opioids. Since cAMP-related events influence the activity of the Na Pump and its biochemical correlate Na,K-ATPase in many systems, we tested the hypothesis that prostaglandin E 1 and [ d-Ala 2, N-Me-Phe 4,Gly 5-ol]-enkephalin (DAMGO), a mu-opioid agonist, have opposing actions on Na,K-ATPase activity. Studies were conducted with alamethicin-permeabilized SH-SY5Y human neuroblastoma cells. Prostaglandin E 1 (1 μM) transiently inhibited Na,K-ATPase activity for 10–15 min. A direct activator of protein kinase A, 8-Br-cAMP (150 and 500 μM), also inhibited, but more rapidly and for a shorter duration. Both DAMGO (1 μM) and Rp-adenosine 3′,5′-cyclic monophosphorothioate (500 μM), a protein kinase A-inhibitor, reversed the inhibitory effect of prostaglandin E 1. DAMGO alone (1 μM) stimulated Na,K-ATPase activity up to nearly three-fold control activity. The stimulatory action of DAMGO was blocked by cyclosporine A (2 μM), an inhibitor of calcineurin, and was dependent on Ca 2+ entry through nifedipine-sensitive Ca 2+ channels. In the presence of 1 mM EGTA, DAMGO inhibited Na,K-ATPase activity. DAMGO-induced inhibition was blocked by the inositol 1,4,5-trisphosphate receptor antagonist xestospongin C (1 μM). Na,K-ATPase is poised to modulate neuronal excitability through its roles in maintaining the membrane potential and transmembrane ion gradients. The differential effects of prostaglandin E 1 and opioids on Na,K-ATPase activity may be related to their actions in hyperalgesia.