Stimulation of cyclic adenosine 3′:5′-monophosphate and corticosterone formation in isolated rat adrenal cells by cholera ente rotoxin comparison with the effects of ACTH

Abstract

1.1. The production of cyclic adenosine 3′:5′-monophosphate (cyclic AMP) and corticosterone in isolated rat adrenal cells was increased by cholera enterotoxin. Both responses were accompanied by a lag period which is characteristic of other known actions of enterotoxin. The duration of the lag period in the production of corticosterone depended on the concentration of enterotoxin; with the maximally stimulating amounts it was 30–45 min.2.2. Maximum rates of cyclic AMP and corticosterone synthesis, after the lag period, were constant for at least 1 h. Although the maximum rate of corticosterone formation was the same as that obtained with adrenocorticotropic hormone, the maximum rate of cyclic AMP formation was only 8–10% of that with adrenocorticotropic hormone.3.3. Pretreatment of the cells with enterotoxin had no effect on their subsequent steroidogenic response to maximally stimulating amounts of adrenocorticotropic hormone.4.4. Cycloheximide inhibited the effect of both enterotoxin and adrenocorticotropic hormone on corticosterone production.5.5. Enterotoxin stimulation of both cyclic AMP and corticosterone formation was dependent on the presence of Ca2+ in the medium although the Ca2+ requirement was not same as that for adrenocorticotropic hormone. Thus, EGTA at concentrations which completely abolished the effect of adrenocorticotropic hormone caused only a partial reduction in the effects of enterotoxin.6.6. Exogenously added choleragenoid and gangliosides abolished the effects of enterotoxin without having any significant effect on the response of the cells to adrenocorticotropic hormone.7.7. After treatment with neuraminidase, the adrenal cells showed an increased response to enterotoxin in terms of both cyclic AMP and corticosterone formation which was due to a combination of two effects: (a) increased rate of synthesis of both compounds and (b) shortening of the characteristic lag period. This is in sharp contrast to the results obtained with adrenocorticotropic hormone where neuraminidase-treatment made the cells less sensitive to adrenocorticotropic hormone.