Inhibition of Ca++-ATPase of rat erythrocyte membranes by k-opioid agonists.
The effect of various opioid agonists on Ca++, Mg++-ATPase activity of rat erythrocyte membranes was studied. The Ca++-stimulated component of this enzyme (Ca++-ATPase) showed properties similar to those of the Ca++-pumping ATPase of human erythrocyte membranes, that is, high affinity for Ca++, potentiation by calmodulin, and insensitiveness to Na+. Ethylketocyclazocine (EKC) dose-dependently inhibited this Ca++-ATPase activity at a concentration less than one nM without changing basal Mg++-ATPase activity and this action was reversed by the antagonist Win 44,441. Other opioid agonists mimicked this EKC effect and the rank order of potency was dynorphin (1-13) = greater than EKC greater than levorphanol = morphine = B-endorphin = dihydromorphine greater than leu-enkephalin greater than (D-Ala)2-(D-leu)5-enkephalin (DADL) = morphiceptin. It is concluded that rat erythrocyte membranes possess k-type opioid receptors through which the Ca++-pump is inhibited.
Yamasaki
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D000818:Animals; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors*; D003496:Cyclazocine / Q000031:analogs & derivatives / Q000494:pharmacology; D004399:Dynorphins / Q000494:pharmacology; D004723:Endorphins / Q000494:pharmacology*; D004910:Erythrocyte Membrane / Q000201:enzymology*; D016314:Ethylketocyclazocine; D007981:Levorphanol / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000187:drug effects* / Q000502:physiology; D017473:Receptors, Opioid, kappa; D001615:beta-Endorphin
D004723:Endorphins; D010446:Peptide Fragments; D011957:Receptors, Opioid; D017473:Receptors, Opioid, kappa; D007981:Levorphanol; D016314:Ethylketocyclazocine; D001615:beta-Endorphin; C026843:dynorphin (1-13); D004399:Dynorphins; D000252:Calcium-Transporting ATPases; D003496:Cyclazocine