Modulation of Na, K-ATPase activity by prostaglandin E1 and [D-Ala2,N-Me-Phe4,Gly5-ol]-enkephalin.
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 E1 and [D-Ala2,N-Me-Phe4,Gly5-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 E1 (1 microM) transiently inhibited Na,K-ATPase activity for 10-15 min. A direct activator of protein kinase A, 8-Br-cAMP (150 and 500 microM), also inhibited, but more rapidly and for a shorter duration. Both DAMGO (1 microM) and Rp-adenosine 3',5'-cyclic monophosphorothioate (500 microM), a protein kinase A-inhibitor, reversed the inhibitory effect of prostaglandin E1. DAMGO alone (1 microM) stimulated Na,K-ATPase activity up to nearly three-fold control activity. The stimulatory action of DAMGO was blocked by cyclosporine A (2 microM), an inhibitor of calcineurin, and was dependent on Ca2+ entry through nifedipine-sensitive Ca2+ 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 microM). 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 E1 and opioids on Na,K-ATPase activity may be related to their actions in hyperalgesia.
Woolcock
Karen
K
University of Puerto Rico School of Medicine, Institute of Neurobiology and Department of Pharmacology and Toxicology, San Juan, 00901, Puerto Rico.
Specht
Susan C
SC
D000527:Alprostadil / Q000494:pharmacology*; D020746:Calcium Channels, L-Type / Q000378:metabolism; D045744:Cell Line, Tumor; D000242:Cyclic AMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)- / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D017450:Receptors, Opioid, mu / Q000819:agonists*; D015398:Signal Transduction / Q000187:drug effects; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism*
D020746:Calcium Channels, L-Type; D004791:Enzyme Inhibitors; D017450:Receptors, Opioid, mu; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D000242:Cyclic AMP; D000254:Sodium-Potassium-Exchanging ATPase; D000527:Alprostadil