Effect of inhibitors of cyclic nucleotide phosphodiesterases on electrical and contractile activity of smooth muscle cells.

Double sucrose gap experiments were carried out to study the effect of phosphodiesterase inhibitors and penetrating analogs of cyclic nucleotides on action potential and contraction of guinea pig ureteral smooth muscle cells. 3-Isobutyl-1-methylxanthine (10 microM) and dibutyryl-cAMP (20 microM) shortened the plateau of action potential and inhibited contraction of smooth muscle cells by increasing potassium permeability of their membrane. Vinpocetine (1 microM) and dibutyryl-cAMP (100 microM) strengthened contraction of smooth muscle cells and shortened action potentials by decreasing sodium permeability of their membrane.