REGIONAL DIFFERENCE OF ENDOGENOUS ATP RELEASE IN THE PULMONARY-ARTERYOF RABBITS

1. The release of adenyl purines such as ATP, ADP, AMP and adenosine, from the pulmonary artery trunk (PAT), extrapulmonary artery (EPA) and intrapulmonary artery (IPA) were compared. 2. The amount of basal ove rflow of adenyl purines from the PAT was significantly smaller than th ose from EPA and IPA, There was no significant difference between the amount of the overflow from EPA and PAT. 3. Methoxamine, an alpha(1)-a drenoceptor agonist, significantly increased the overflow of adenine n ucleotides from the PAT, EPA and IPA, but did not increase those of ad enosine. Methoxamine-induced release of adenyl purines from IPA was si gnificantly larger than those from EPA and PAT. 4. These results sugge st that an alpha(1)-adrenoceptor-mediated mechanism for ATP-release is not homogeneously distributed in the pulmonary artery and a larger am ount of ATP may be released in the peripheral part of the artery.