Methoxamine-induced release of endogenous ATP from rabbit pulmonary artery

Methoxamine, an alpha 1-adrenoceptor agonist, significantly increased the overflow of ATP, ADP and AMP, but not adenosine, by a prazosin-sensitive mechanism in the rabbit pulmonary artery. Among the adenine nucleotides released, the amount of ATP was larger than those of the other two. Such release of adenine nucleotides was not induced by clonidine, an alpha 2-adrenoceptor agonist, and isoproterenol, a beta-adrenoceptor agonist. Methoxamine-induced release was observed in the absence of extracellular calcium, but was not observed at a low temperature, 27 degrees C. This suggests an extracellular calcium-independent and temperature-dependent ATP-releasing mechanism coupled with alpha 1-adrenoceptors in rabbit pulmonary artery.