Adrenocortical function in a new world primate, the marmoset monkey, Callithrix jacchus

The function of the adrenal cortex of the marmoset monkey Callithrix jacchus has been investigated. In common with other New World primates, these animals seem to be glucocorticoid resistant. Blood and adrenal glands were obtained from male and female animals under terminal pentobarbitone anesthesia. Dispersed adrenal cell preparations were obtained by treatment with collagenase and incubated with ACTH(1-24), (0.1-1000 nM) angiotensin II (0.1-1000 nM), dibutyryl cyclic AMP (dbcAMP; 30-1000 microM), and forskolin (FSK; 1-30 microM). Plasma cortisol levels (2113 +/- 449 ng/ml male; 3858 +/- 429 ng/ml female) were found to be 10- to 20-fold higher than those quoted for Old World primates and man. The cell preparations showed no significant response to any dose of ACTH tested (0.1-1000 nM), although addition of exogenous precursor (22R-hydroxycholesterol, 2.5 microM) resulted in an increased yield of cortisol and aldosterone. Cyclic AMP production was increased in response to forskolin (1-30 microM) but not ACTH(1-24) (1-1000 nM). In addition, dose-related responses to angiotensin II (maximal stimulation of 316 +/- 49% basal aldosterone at 100 nM angiotensin II), dbcAMP (maximal stimulation of 449 +/- 24% basal cortisol at 300 microM dbcAMP), and forskolin (maximal stimulation of 394 +/- 31% basal cortisol at 10 microM FSK) were obtained. The lack of a response in vitro to ACTH in C. jacchus cannot, therefore, be attributed either to general failure of the cells or to defects in postreceptor signaling mechanisms. The results suggest that there is a reduction in adrenal ACTH receptor number or affinity, with a high basal production rate in vivo maintaining the elevated plasma cortisol levels.