ACTH-induced change of cAMP-dependent protein-kinase repartition in bovine adrenal cells

Abstract

Acute ACTH stimulation of isolated adrenal cells produced a modification of the subcellular distribution of cAMP-dependent protein kinase. Within 20 min, the protein-kinase ratio in all subcellular fractions, particularly in the 175000 × g supernatant, was increased. Total protein-kinase activity, as well as the specific activity of both the homogenate and particulate enzymatic activities, was decreased while that of the 175000 × g supernatant was increased. However, the increase of the soluble kinase activity represented only 29–46% of the lost particulate activity. On the other hand, under exchange conditions, the cAMP-binding capacity of all subcellular fractions was similar in control and ACTH-treated cells, except in the 175 000 × g pellet in which it was slightly decreased in ACTH-treated cells. These modifications were observed for supraphysiological (10 −8M), as well as for physiological (10 −11M), concentrations of ACTH. These observations suggest that, after ACTH stimulation, a liberation of free catalytic sub-unit occurs from particulate into the soluble cell compartment, which shows an activation of particulate cAMP-dependent protein-kinase activity.