Involvement of the cytoskeleton in the steroidogenic response of frog adrenal glands to angiotensin II, acetylcholine and serotonin.

In order to determine the role of the cytoskeleton in adrenal steroidogenesis, we have studied the effect of cytochalasin B (a microfilament-disrupting agent) and vinblastine (an antimicrotubular drug) on corticosteroid secretion by frog interrenal tissue in vitro. Perifusion of interrenal fragments with cytochalasin B (50 mumol/l) induced a marked inhibition of basal corticosteroid output. In addition, stimulation of corticosteroidogenesis by all corticotrophic factors was also inhibited by cytochalasin B. Using an immunohistochemical technique and specific anti-tubulin antiserum, we verified that vinblastine (10 mumol/l) was responsible for the disappearance of the microtubular network in adrenocortical cells. Administration of vinblastine (10 mumol/l) did not affect the spontaneous secretion of corticosterone and aldosterone and had no effect on the steroidogenic response of interrenal glands to angiotensin II and acetylcholine. In contrast, vinblastine was responsible for a marked decrease in serotonin-induced stimulation of corticosteroid production. On the other hand, data from high-performance liquid chromatography showed that infusion of cytochalasin B or vinblastine was not associated with the production of any new steroid which could interfere in the radioimmunoassays. Taken together, these data suggest that microfilaments are involved in a late and common step of corticosteroidogenesis while microtubules are only required for the coupling of the secretory response to certain corticotrophic factors such as ACTH and serotonin.