Physiological calcium ion concentration and a cholinergic drug on activity of particulate guanylate cyclase in guinea pig taenia caecum.

The microsomal fraction derived from the taenia caecum of guinea pigs was used as particulate guanylate cyclase preparation. The guanylate cyclase activity was not influenced by butyltrimethylammonium bromide and Ca2+ (4.0 to 24 X 10-7 M). The results suggest that the particulate guanylate cyclase is not activated by the drug-receptor interaction and also by the increase of intracellular Ca2+ concentration. Therefore, the increase of tissue level of cyclic GMP brought about in the guinea pig taenia caecum might be due to activation of soluble guanylate cyclase following the increase in the intracellular Ca2+ concentration.