Morphological correlates of adrenocorticotropin-stimulated steroidogenesis in cultured adrenocortical cells: differences between bovine and human adrenal cells.

ACTH causes dramatic morphological changes in cultured adrenocortical cells of several species. In the present study, the morphological changes induced by ACTH in primary bovine and human fetal adrenocortical cells have been examined. Both cell types responded similarly in their ACTH-stimulated increase in steroidogenesis and ACTH inhibition of cell proliferation. However, they differed in their morphological responses. Epithelial-like human fetal adrenal cells became round and lost substrate attachment as a result of ACTH treatment, whereas similarly treated cultured bovine adrenal cells did not. Observation of actin distribution using 7-nitrobenz-2-oxa-1,3-diazolephallacidin and fluorescence microscopy revealed a loss of stress fibers in the human cells treated with ACTH, but little or no effect in identically treated bovine cells. Because of the similar biochemical responses but different morphological responses in these cells, we suggest that the steroidogenic and retraction responses to ACTH are separable events.