Steroidogenic properties of isolated turkey adrenocortical cells

Abstract

Some functional properties of highly enriched turkey poult adrenocortical cells were characterized. Cells were incubated with various mammalian and avian ACTH analogues, 8-Br-cAMP, and 25-hydroxycholesterol for 2 hr. Corticosterone production and, where appropriate, cyclic AMP (cAMP) production were measured by radioimmunoassay. Human ACTH-(1–24) was the most efficacious and potent ACTH analogue for stimulating corticosterone and cAMP production, whereas turkey ACTH-(1–39) was among the least efficacious and least potent analogues. Maximal corticosterone production induced by 8-Br-cAMP and supported by 25-hydroxycholesterol was 67–109% greater than that induced by ACTH analogues. The data suggest that intracellular concentrations of cAMP-dependent factors and steroidogenic enzymes exceed those which are accessible to ACTH-activated cellular processes. In addition, there were sex-dependent contrasts in some functional parameters, despite the immature status of the birds. Basal corticosterone production of female cells was 19% greater than that of male cells, albeit maximal ACTH analogue-induced corticosterone production was not different between male and female cells. In contrast, maximal 8-Br-cAMP-induced and 25-hydroxycholesterol-supported corticosterone production of male cells were, respectively, 72 and 45% greater than that of female, cells, thus suggesting greater intracellular concentrations of protein kinase A-dependent factors and steroidogenic enzymes in male cells compared to female cells. However, maximal ACTH-induced cAMP production of female cells was 21% greater than those of male cells, thus suggesting a compensatory mechanism in female cells. In addition, there were sex-dependent differences in sensitivity to ACTH as indicated by corticosterone and cAMP responses to ACTH analogues: sensitivity of male cells was 1.2–3.2 times that of female cells. A sex-dependent difference in ACTH-cell interaction, possibly including ACTH receptors, is implicated since there were no sex differences in cellular sensitivities to 8-Br-cAMP and 25-hydroxycholesterol. These data indicate that the turkey adrenal gland is amenable for the preparation of isolated adrenocortical cells that have functional integrity. Thus, turkey adrenocortical cells expand the in vitro repertoire for elucidating the regulatory mechanisms of avian adrenocortical function.