Distinct mechanisms underlying alpha1-adrenoceptor and P2x purinoceptor operated ATP release and contraction in the guinea-pig vas deferens.
The temperature-dependence of ATP release and contraction response evoked by different agonists were investigated in superfused guinea-pig vas deferens. Alpha-adrenoceptor agonists, i.e. noradrenaline (300 microM), and alpha-methyl-noradrenaline (300 microM), increased the basal ATP outflow, measured by the luciferin-luciferase assay, and induced biphasic contractile response. Cooling the bath temperature to 12 degrees C almost completely inhibited ATP release and twitch contraction evoked by alpha-adrenoceptor agonists, whereas the phasic contraction remained unaffected. In contrast, twitch contraction and subsequent ATP release induced by beta,gamma-methylene-ATP, a selective P2 receptor agonist (100 microM), was not reduced by low temperature. The ectoATPase activity, measured by HPLC technique was not significantly different at 37 degrees C and 12 degrees C. Nifedipine (1 microM), the voltage sensitive Ca2+ channel blocker eliminated beta,gamma-methylene-ATP evoked twitch contraction but not ATP release. In conclusion, alpha-adrenoceptor and P2 receptor agonists utilize distinct mechanisms to elicit ATP release and contraction: alpha-adrenoceptor-mediated ATP release and contraction is temperature-dependent, indicating the involvement of a carrier-mediated process in it, whereas P2x purinoceptor evoked ATP release and twitch is mediated by a different mechanism.
Sperlágh
B
B
Department of Pharmacology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest. sperlagh@koki.hu
Illes
P
P
Gerevich
Z
Z
Köfalvi
A
A
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction; D018340:Receptors, Adrenergic, alpha-1 / Q000502:physiology*; D018048:Receptors, Purinergic P2 / Q000502:physiology*; D058469:Receptors, Purinergic P2X; D014649:Vas Deferens / Q000378:metabolism* / Q000502:physiology
D018340:Receptors, Adrenergic, alpha-1; D018048:Receptors, Purinergic P2; D058469:Receptors, Purinergic P2X; D000255:Adenosine Triphosphate