[Dissociation of the action of isoprenaline on muscle tension and adenosine-3',5'-monophosphate synthesis in isolated coronary arteries under the effect of diisopropylfluorophosphate].

The basal activity of a particulate adenylate cyclase from bovine coronary arteries was inhibited by low concentrations of diisopropyl-fluorophosphate (DFP), paraoxon and dimethoate. The formation of 14C-labelled cAMP in coronary vessels pulse-labelled with 14C-adenine was inhibited by DFP, too. The stimulating effect of isoprenaline on the cAMP synthesis was completely abolished by DFP both in the cell free system and in pulse-labelled artery preparations. Cholinergic mechanisms are not involved in these actions of DFP because pretreatment with atropine had no influence. DFP both reduced the basal level and completely inhibited the isoprenaline-induced increase of the cyclic AMP content of coronary vessels. In contrast to the biochemical findings there was no observable influence of DFP on the smooth muscle tension or on the relaxation induced by isoprenaline, papaverine and theophylline. The total dissociations of isoprenaline-induced effects on the vascular cAMP system and on smooth muscle tension under the influence of DFP disagree with the opinion according to which beta-adrenergic vascular relaxation is mediated by cAMP.