Comparison of the Effects of Adrenocorticotropic Hormone on the Steroidogenic Activity and Ultrastructure of -4drenal Cortex*

Comparison of ultrastructural and biochemical response to adrenocorticotropic hormone (ACTH) in superfused adrenals or cell suspension and in adrenals of hypophysectomized rats showed that (a) steroidogenic response can take place in superfused glands that have suffered gross structural damage and contained no detectable intact mitochondria; (b) steroidogenesis of cell suspensions takes place without dilation of the endoplasmic reticulum; (c) adrenals of l-day posthypophysectomized rats respond normally to ACTH in terms of ultrastructural changes even though they have lost their responsiveness to ACTH in terms of steroidogenesis; (d) these ACTH-induced ultrastructural changes in adrenals of hypophysectomized rats are blocked by the prior administration of cycloheximide and postulated to be dependent upon the translation of preformed mRNA with a longer halflife than the mRNA coding for the labile steroidogenic protein.