ELECTROPHYSIOLOGICAL AND FUNCTIONAL-EFFECTS OF ADENOSINE ON VENTRICULAR MYOCYTES OF VARIOUS MAMMALIAN-SPECIES

The goal of this study was to determine the electrophysiological and f unctional effects of adenosine on ventricular myocytes of guinea pig, rabbit, rat, and ferret hearts. Adenosine (100 mu M) shortened the act ion potential durations of rat and ferret myocytes by 14 +/- 1 and 57 +/- 7%, reduced the amplitudes of cell twitch shortening by 13 +/- 1 a nd 54 +/- 5%, and increased outward currents by 15 +/- 4 and 55 +/- 5% , respectively, but had no effect on guinea pig and rabbit myocytes. T he properties of adenosine-activated outward current in rat and fer re t ventricular myocytes indicated that this current is the adenosine-se nsitive K+ current [I-K(Ado)] Adenosine had no significant effect on b asal Ca2+ current but specifically inhibited isoproterenol-stimulated L-type Ca2+ current in myocytes of all species studied. Binding studie s revealed that the density of Al adenosine receptors (A(1)AdoR) was h ighest in ferret and lowest in rabbit myocytes, but the differential e ffects of adenosine among species could not be solely explained by dif ferences in A(1)AdoR density. In summary, adenosine shortened the acti on potential and reduced the twitch shortening of rat and ferret but n ot of guinea pig and rabbit ventricular myocytes. Shortening of the ac tion potential was associated with the activation of I-K(Ado) The anti -beta-adrenergic action of adenosine appeared to be independent of spe cies.