P2X-purinoceptors in the heart: actions of ATP and UTP.
Positive inotropic effects of ATP and UTP (1 microM - 1mM) were studied in isolated rat and guinea pig cardiac tissues. The potency order obtained was ATP>UTP in both species, suggesting possible interaction with P2X-purinoceptors. Binding studies using [(3)H]alpha,beta-methylene ATP as marker of P2X-purinoceptors revealed two receptor sites: one high-, the other low-affinity, in atria and ventricles from rat and guinea pig. Both ATP and UTP were found to bind high-affinity sites of [(3)H]alpha,beta-methylene ATP. The effects of various calcium inhibitors such as nifedipine, dantrolene, ryanodine and TMB-8 on positive inotropic effects induced by ATP and UTP were also studied. The results suggest that ATP and UTP may increase inotropism by interaction with P2X-purinoceptors by means of a calcium-dependent mechanism.
Froldi
G
G
Department of Pharmacology, University of Padova, Italy. mina@dfem.unipd.it
Varani
K
K
Chinellato
A
A
Ragazzi
E
E
Caparrotta
L
L
Borea
P A
PA
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism*; D000818:Animals; D001667:Binding, Competitive; D002118:Calcium / Q000378:metabolism; D006168:Guinea Pigs; D007700:Kinetics; D009119:Muscle Contraction; D009206:Myocardium / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D013268:Stimulation, Chemical; D014544:Uridine Triphosphate / Q000378:metabolism*
D018048:Receptors, Purinergic P2; D000255:Adenosine Triphosphate; C002630:alpha,beta-methyleneadenosine 5'-triphosphate; D002118:Calcium; D014544:Uridine Triphosphate