Effect of growth hormone and corticotropin on steroidogenesis in cultured rat adrenocortical cells.

Primary cultures of rat adrenocortical cells responded to corticotropin (ACTH; 10 microU/ml) with peak steroid production within 24 h which declined thereafter. In the presence of ACTH and growth hormone (GH; 10 micrograms/ml), steroid production was significantly greater than with ACTH alone and was better maintained over several days. This latter response was not due to changes in cell number or multiplication and required several days to develop. GH also interacted with 10(-6) and 10(-5) M dibutyryl cyclic AMP (dbcAMP) to augment synthesis of corticosterone. At maximal doses of both ACTH and dbcAMP, GH did not have an additional effect on steroid production. In conclusion, GH has a stimulatory effect on steroid production when added in vitro but it is unlike the response seen in vivo in that it is less sensitive, additive rather than synergistic, and without effect on cell growth and multiplication.