INVOLVEMENT OF THE CYTOSKELETON IN THE MECHANISM OF ACTION OF ENDOTHELIN ON FROG ADRENOCORTICAL-CELLS

In a previous report, we have shown that endothelin-1 (ET-1) is a pote nt stimulator of corticosterone and aldosterone secretion by frog adre nocortical cells. In the present study, we examine the possible involv ement of cytoskeletal elements in the mechanism of action of ET-1 on c orticosteroid secretion from frog adrenal gland. The microfilament dis rupting agent cytochalasin B (5 x 10(-5) M) induced a reversible inhib ition of the spontaneous secretion of corticosteroid and blocked the r esponse of adrenocortical cells to ET-1 (5 x 10(-9) M). In contrast, t he antimicrotubular agent vinblastine (10(-5) M) and the intermediate filament inhibitor beta-beta' iminodipropionitrile (10(-3) M) had virt ually no effect on both spontaneous and endothelin-induced steroidogen esis. Taken together, these results indicate that, in the frog adrenal gland, the integrity of the microfilament network is required for the corticotropic activity of ET-1 whereas microtubules and intermediate filaments are apparently not involved in the mechanism of action of ET -1.