title: Adenosine A1 receptor stimulation antagonizes the negative inotropic effects of the PKC activator dioctanoylglycerol.
abstract: It has been suggested that adenosine cardioprotection occurs via adenosine A1 receptor-mediated activation of protein kinase C (PKC). However, adenosine has well-known vasodilatory effects in the myocardium, whereas PKC is a vasoconstrictor. This study examined whether adenosine A1 receptor activation alters the effects of the PKC activator. 1,2-dioctanoyl-s,n-glycerol (DOG) in isolated perfused rat hearts (left-ventricular developed pressure) and rat ventricular myocytes ([Ca2+]i and cell shortening). Exposure to DOG decreased left-ventricular developed pressure by 30%, an effect that was completely reversible. Pretreatment of isolated hearts with either the PKC inhibitor chelerythrine or the adenosine A1 agonist 2-chloro-N6-cyclo-cyclo-isolated pentlyadenosine (CCPA) attenuated the negative inotropic effects of DOG. In the isolated myocytes, DOG decreased [Ca2+]i and cell shortening by 25 and 28%, respectively, effects that were attenuated by both chelerythrine and CCPA. The CCPA attenuation of the DOG-induced decrease in [Ca2+]i and cell shortening was blocked by pretreating the myocytes with the adenosine A1 antagonist, 8-cyclopentyl-1,3-dipropylxanthine (DPCPX). These results indicate that in rat ventricular myocardium, adenosine A1 receptor activation attenuates the apparent PKC-dependent negative inotropic effects of DOG via preservation of [Ca2+]i levels.
authors.affiliation: Department of Surgery, University of Kentucky College of Medicine, Lexington 40536, USA.
authors.forename: P
authors.initials: P
authors.lastname: Narayan
authors.forename: H H
authors.initials: HH
authors.lastname: Valdivia
authors.forename: R M
authors.initials: RM
authors.lastname: Mentzer
authors.forename: R D
authors.initials: RD
authors.lastname: Lasley
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D003864:Depression, Chemical; D004075:Diglycerides / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D004789:Enzyme Activation; D006352:Heart Ventricles / Q000166:cytology / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D058906:Purinergic P1 Receptor Agonists; D051381:Rats; D017207:Rats, Sprague-Dawley; D013268:Stimulation, Chemical; D014970:Xanthines / Q000494:pharmacology
chemical_list: D004075:Diglycerides; D058906:Purinergic P1 Receptor Agonists; D014970:Xanthines; C044295:1,2-dioctanoylglycerol; C058394:2-chloro-N(6)cyclopentyladenosine; C051360:1,3-dipropyl-8-cyclopentylxanthine; D000241:Adenosine