Influence of phenylephrine on levels of cyclic 3',5'-AMP in the heart of rats in vivo.

In the course of an investigation into the mode of action of phenylephrine using the radioimmunoisotope method, its influence on levels of cyclic 3'5'-AMP in the heart of rats was studied. Phenylephrine in the dose of 1 microgram/kg/min after five minutes lowered levels of this nucleotide by about 20%. Phenylephrine also inhibited the influence of theophyline, an inhibitor of phosphodiesterase which raises levels of c-AMP. The results suggest that the drop in c-AMP after phenylephrine is connected with lowered activity of adenyl cyclase, but do not exclude the possiblity of an interaction between theophylline and phenylephrine acting on phosphodiesterase, which could be referred to the observed effect.