Cyclic AMP and the potassium-induced vasodilation

The cAMP concentration of bovine facial arteries (helical strips) increased from 0.84 +/- 0.14 to 1.51 +/- 0.24 nmole/g wet weight, when the strips were relaxed by exposure to a physiological salt solution containing 10 instead of 2.7 mM KCl. A similar result (increase from 1.13 +/- 0.15 to 2.07 +/- 0.29 nmole cAMP/g wet weight) was obtained in strips pretreated with 10(-7) g/ml beta-methyldigoxin. These strips reacted to 10 mM KCl with a constriction. Addition of the phosphodiesterase activator N-methyl-imidazole (3 - 10(-3)M) did not affect the mechanical response to 10 mM KCl. It is concluded that for the potassium-induced vasodilation cAMP does not have a mediating function comparable to that in beta-adrenergic relaxation of vascular smooth muscle.