Adenosine 3':5'-Monophosphate Binding Activity and Guanosine 3':5'-Monophosphate Binding Activity during Adrenocorticotropic Hormone Stimulation in Rat Adrenal Gland

Abstract

The effect of adrenocorticotropic hormone (ACTH) on the change in adenosine 3':5'-monophosphate (cyclic AMP) binding activity and guanosine 3':5'-monophosphate (cyclic GMP) binding activity in adrenal glands of hypophysectomized rats was examined by measuring cyclic [³H] AMP-binding and cyclic [³H] GMP-binding, respectively. When ACTH_1-24-retard (200 μg/100g body weight/day) was injected into rats for 3 days, the increase in cyclic AMP-binding activity (activity/100g body weight) found in the supernatants, mitochondria, and microsomes of adrenal glands was greater than the growth of adrenal glands, whereas the increase in cyclic GMP-binding activity (activity/100g body weight) was almost equal to that of adrenal size. Administration of less than 200 μg ACTH_1-24-retard did not effectively stimulate both activities. During 3 days, a mixture of ACTH_1-24-retard and -immediate (200 μg and 5 U/100g body weight/day) induced increases of 2.8-fold in adrenal weight, 6.0-, 1.5-, and 5.8-fold in cyclic AMP-binding activity and 1.3-, 1.3-, and 2.1-fold in cyclic GMP-binding activity in the supernatants, microsomes, and mitochondria, respectively. In regard to the effect of the ACTH_1-24-mixture on the specific activity (activity/μg protein), the activity of the cyclic AMP-binding protein increased in supernatants and mitochondria but not in microsomes, whereas that of the cyclic GMP-binding protein decreased in all three subcellular fractions. The effect of administration of the ACTH_1-24-mixture for 9 days was marked on the stimulation of cyclic AMP-binding activity, while the specific activity was not significantly affected. These results indicated the presence of a differential effect on the cyclic AMP- and cyclic GMP-binding activities during ACTH action, and suggested that both cyclic AMP- and cyclic GMP-binding proteins may be involved in ACTH action and play an important role in hormonal control of steroidogenesis through regulation of the adrenal cortex.