[Effect of adenosine, AMP and papaverine on the cAMP content in thymocytes prelabelled with 14C-adenine].

A study was made of the effects of adenosine, AMP and papaverine on the content and specific radioactivity of cAMP and ATP in rat thymocytes prelabeled with 14C-adenine. It was established that each of the substances under study increases approximately 2-fold the intracellular cAMP content. Adenosine or AMP combined with papaverine raises the cAMP level more powerfully than it might be expected as a result of such an ordinary summation. Being cAMP precursors adenosine or AMP increase its level in thymocytes. However in the presence of papaverine they exercise their action via adenylate cyclase. Thymocytes demonstrate two ATP compartments prelabeled mainly with 14C-adenine relative to the general cellular ATP and are used for cAMP formation. The compartment with a greater specific radioactivity gives rise to cAMP in thymocytes incubated in the absence of effectors or upon addition of papaverine. The compartment having a lesser specific radioactivity serves as ATP source for adenosine or AMP-sensitive adenylate cyclase and rapidly catabolizes under the effect of papaverine.