Activity of guanylate cyclase of various tissues and its in vitro modulation by effectors as a function of age of rats

Abstract

The activities of guanylate cyclase of the soluble, microsomal, mitochondrial and nuclear fractions of the cerebral cortex, heart and lungs of 4- (young), 34- (adult) and 85-week-old male rats were studied. The effects of aminophylline, histamine and estradiol on the enzyme were also determined. The activity of the enzyme is high in the particulate fractions of the heart and lungs in all the ages, but in the cerebral cortex, the activity is high in the soluble fraction of young and old rats. Its activity is the highest in all the fractions of all the tissues of adult rats, except that of the soluble fraction of the cerebral cortex in which it is lowest at this age. The particulate and soluble guanylate cyclase of the cerebral cortex, heartand lungs have different sensitivities to aminophylline, histamine and estradiol in vitro. In general, its sensitivity to the three effectors is the lowest in old age.