Comparison of Steroidogenic Effects of cAMP and dbcAMP in the Rat Adrenal Gland1 1

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Abstract
The steroidogenic response of superfused rat adrenal quarters to ACTH and cAMP began after a lag period of 3.3 =t 0.5 and 3.0 ± 0.3 min, respectively. The lag period with dbcAMP was 6.0 ± 0. 7 min. In all cases the lag period was independent of the dose of the stimulant. The current theory of the mode of action of ACTH and cAMP postulates that cAMP promotes the synthesis of a labile regulatory protein that in turn accelerates steroidogenesis. If the synthesis of protein accounts for most of the lag period, the size of the protein can be estimated to be 14,000 to 200,000 daltons. 3H from labelled cAMP entered adrenal tissue more rapidly than 3H from dbcAMP. Therefore, the greater potency of dbcAMP in stimulating steroidogenesis cannot be explained solely by a faster rate of penetration. The cAMP was almost completely changed to adenosine and nucleotides; dbcAMP was virtually unchanged. Maximal stimulation of superfused adrenal quarters by dbcAMP (1.2 X 10∼4JVI) caused a rate of steroidogenesis 30% lower than maximal stimulation by either ACTH (3 X 10-7M) or cAMP (9 X 10-3M). When dbcAMP was added to adrenals already maximally stimulated with either ACTH or cAMP, the rate of steroidogenesis decreased to the same level as that produced by dbcAMP alone. These observations are discussed in terms of competition between cAMP and dbcAMP for a common active site within the adrenocortical cell. (Endocrinology92: 679, 1973)

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