Dual effect of ATP and UTP on rat atria: which types of receptors are involved?
The effects of adenine compounds and UTP were examined in electrically driven rat left atria. ATP, ADP, AMP, adenosine and UTP caused a dual inotropic effect: first a rapid decrease in contractility, and second an increase in contractile tension. alpha,beta-Methylene ATP caused an increase in contractile tension only, whereas 2-methylthio-ATP only induced a negative inotropic effect, 1,3-Dipropyl-8-cyclopentylxanthine inhibited the negative effects of ATP and adenosine, whereas 3,7-dimethyl-1-propargylxanthine did not influence the effects of ATP. Suramin but not reactive blue 2 antagonized the positive inotropism induced by ATP and alpha,beta-methylene ATP. Suramin also abolished the positive inotropic effect induced by UTP. These results demonstrate that ATP may induce negative inotropism directly by an action on A1-adenosine receptors and positive inotropism by an action on P2x-purinoceptors. UTP induces a positive inotropic effect mediated by suramin-sensitive receptors.
Froldi
G
G
Department of Pharmacology, University of Padova, Italy.
Pandolfo
L
L
Chinellato
A
A
Ragazzi
E
E
Caparrotta
L
L
Fassina
G
G
D000243:Adenosine Deaminase / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology*; D000818:Animals; D006321:Heart / Q000187:drug effects*; D006325:Heart Atria / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D058915:Purinergic P1 Receptor Antagonists; D058919:Purinergic P2 Receptor Antagonists; D051381:Rats; D017208:Rats, Wistar; D018047:Receptors, Purinergic P1 / Q000187:drug effects*; D018048:Receptors, Purinergic P2 / Q000187:drug effects*; D013268:Stimulation, Chemical; D013498:Suramin / Q000494:pharmacology; D014530:Uridine Diphosphate / Q000494:pharmacology*; D014970:Xanthines / Q000494:pharmacology
D058915:Purinergic P1 Receptor Antagonists; D058919:Purinergic P2 Receptor Antagonists; D018047:Receptors, Purinergic P1; D018048:Receptors, Purinergic P2; D014970:Xanthines; D014530:Uridine Diphosphate; D013498:Suramin; D000255:Adenosine Triphosphate; C051360:1,3-dipropyl-8-cyclopentylxanthine; D000243:Adenosine Deaminase; C002630:alpha,beta-methyleneadenosine 5'-triphosphate