Possible involvement of Ca2+-calmodulin system in cyclic AMP action in cholesterol ester hydrolytic response to ACTH in bovine adrenocortical cells.

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Abstract
In order to elucidate the relationship between cAMP and the Ca2+-calmodulin system in the steroidogenic response to ACTH, the effects of calmodulin inhibitors (trifluorperazine and W-7 [N-(6-aminohexyl)-5-chloro-1-naphthalene sulfonamide]) on cortisol production and cellular cholesterol ester hydrolysis induced by ACTH or dibutyryl cAMP in bovine adrenocortical cells were examined in the absence of extracellular Ca2+. These calmodulin inhibitors inhibited not only the cortisol production and the cholesterol ester hydrolysis induced by ACTH in the absence of extracellular Ca2+, but also inhibited the dibutyryl cAMP-induced cortisol production and the cholesterol ester hydrolysis in the absence of extracellular Ca2+. Apparently, cAMP action was mediated by the Ca2+-calmodulin system in the activation process of cellular cholesterol ester hydrolysis in the steriodogenic response to ACTH.