6-Benzylaminopurine: a plant derived cytokinin inducing positive inotropism by P2-purinoceptors.
Positive inotropic effects induced by 6-benzylaminopurine (6-BAP), kinetin and zeatin were studied in rat atria. The potency order observed was 6-BAP > or = kinetin > zeatin. Suramin, a P2-purinoceptor antagonist, inhibited the positive effect of 6-BAP suggesting the involvement of P2-purinoceptors in the positive effect of this cytokinin. In order to elucidate this point, 6-BAP was used against R-PIA (a P1-purinoceptor agonist) and ATP and UTP (both P2-purinoceptor agonists). 6-BAP did not influence negative inotropism by R-PIA whereas both nucleotides were inhibited after pretreatment with the cytokinin. LY 83583, an inhibitor of cGMP production, reduced the inotropic effect by cytokinin whereas L-NAME, an inhibitor of the L-arginine/nitric oxide pathway, did not influence the effect induced by 6-BAP. Indomethacin, an inhibitor of cyclooxygenase, and neomycin, an inhibitor of phospholipase C, did not significantly modify positive inotropism by 6-BAP. Verapamil, an inhibitor of L-type calcium channels, did not change the positive effect of 6-BAP while TMB-8 and dantrolene, two inhibitors of intracellular calcium release, reduced the increase of contractile tension induced by cytokinin. Our data on rat atria suggest that 6-BAP causes a positive inotropism through activation of P2-purinoceptors, involving modification of cGMP and of intracellular calcium.
Froldi
G
G
Department of Pharmacology, University of Padova, Italy. froldi@ux1.unipd.it
Gallo
U
U
Ragazzi
E
E
Caparrotta
L
L
D000225:Adenine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D016275:Atrial Function; D001593:Benzyl Compounds; D003583:Cytokinins / Q000096:biosynthesis*; D006325:Heart Atria / Q000187:drug effects*; D066298:In Vitro Techniques; D007701:Kinetin; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D010944:Plants / Q000737:chemistry*; D011687:Purines; D051381:Rats; D017208:Rats, Wistar; D018048:Receptors, Purinergic P2 / Q000502:physiology*
D001593:Benzyl Compounds; D003583:Cytokinins; D011687:Purines; D018048:Receptors, Purinergic P2; D000225:Adenine; C480551:benzylaminopurine; D007701:Kinetin