Cyclic 3′,5′-adenosine monophosphate phosphodiesterase (cAMP PDE) and cyclic 3′,5′-guanosine monophosphate phosphodiesterase (cGMP PDE) in microvessels isolated from bovine cortex

Abstract

It was established that microvessels of a bovine cortex exhibit significant cyclic 3′,5′-adenosine monophosphate phosphodiesterase (cAMP PDE) and cyclic 3′,5′-guanosine monophosphate phosphodiesterase (cGMP PDE) activities. These activities are dependent on the presence of Mg²⁺. Absence of Ca²⁺ was virtually without effect. When both Mg²⁺ and Ca²⁺ were absent, PDE activities increased compared with activities observed in the absence of Mg²⁺. Xanthines (caffeine, theobromine, and theophylline) were better inhibitors of cAMP PDE than of cGMP PDE. Imidazole, in very high concentration (1×10⁻²M) only, exhibited PDE stimulatory activity at high concentrations of both substrates. Otherwise, it exhibited PDE-inhibitory properties.