Opioid receptors in rat cardiac sarcolemma: effect of phenylephrine and isoproterenol.
The present study demonstrates the presence of opioid receptors in the rat cardiac sarcolemma isolated by the hypotonic LiBr-shock procedure. Opioid binding was measured by using [3H]U69 593, [3H](2-D-penicillamine,5-D-penicillamine)enkephalin ([3H]DPDPE) or [3H][D-Ala2,MePhe4,Gly-(ol)5]enkephalin ([3H]DAGO) as selective radioligands for K, delta and mu opioid receptors, respectively. Both the K- and delta-selective ligands exhibited highly specific (75-86%) binding, saturable at a concentration of about 20 nM. No specific binding for the selective agonist DAGO was observed. A marked increase in both [3H]U69 593 and [3H]DPDPE binding was observed after incubation of the sarcolemma with the alpha-adrenoceptor agonist phenylephrine or with the beta-adrenoceptor agonist isoproterenol. These stimulatory effects were associated with an increase in the Bmax values, a decrease in the Kd values, and were completely antagonized by the respective antagonists phentolamine and propranolol.
Ventura
C
C
Department of Biochemistry Centre of Research on Cardiac Metabolism, Bologna, Italy.
Bastagli
L
L
Bernardi
P
P
Caldarera
C M
CM
Guarnieri
C
C
D000700:Analgesics; D000818:Animals; D044482:Benzeneacetamides; D001965:Bromides; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D020881:Enkephalin, D-Penicillamine (2,5)-; D004745:Enkephalins / Q000378:metabolism; D007038:Hypotonic Solutions; D007545:Isoproterenol / Q000494:pharmacology*; D008094:Lithium; D018020:Lithium Compounds; D009206:Myocardium / Q000378:metabolism*; D010656:Phenylephrine / Q000494:pharmacology*; D011759:Pyrrolidines / Q000378:metabolism; D051381:Rats; D011957:Receptors, Opioid / Q000187:drug effects / Q000378:metabolism*; D017465:Receptors, Opioid, delta; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; D012508:Sarcolemma / Q000187:drug effects / Q000378:metabolism*
D000700:Analgesics; D044482:Benzeneacetamides; D001965:Bromides; D004745:Enkephalins; D007038:Hypotonic Solutions; D018020:Lithium Compounds; D011759:Pyrrolidines; D011957:Receptors, Opioid; D017465:Receptors, Opioid, delta; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D010656:Phenylephrine; C040949:lithium bromide; D020881:Enkephalin, D-Penicillamine (2,5)-; D008094:Lithium; C045444:U 69593; D007545:Isoproterenol