Alteration of Vein Cyclic 3':5' Nucleotidc Changes in Contractility*

The relative changes in vascular tissue lev- els of cyclic 3':5'-guanosine monophosphate (cGMP) and cyclic 3' :5'-adenosine monophosphate (cAMP) were deter- mined in bovine and canine vein strips that were quick- frozen during changes in contractility elicited by prosta- glandins (PG) or isoproterenol. Prostaglandin F2m-induced venoconstriction was associated with increased vascular tissue levels of cGMP and increased ratios of cGMP to cAMP concentrations, but no consistent qualitative change in cAMP levels. In contrast, vein cAMP concentrations were increased during administration of the vasodilators PGE2 and isoproterenol. The results suggest possible op- posing roles for the two cyclic nucleotides in vasomotion.