AGEING AND ADRENAL \g=D\5-3\g=b\-HYDROXYSTEROID DEHYDROGENASE IN FEMALE MICE

A decline in rodent adrenal function with ageing has been suggested by reduced adrenal cortico-sterone production in vitro (Nandi, Bern, Biglieri & Pieprzyk, 1967) and corticosterone in the circulation (Grad & Khalid, 1968) of aged female mice, and adrenal \g=D\5-3\g=b\-hydroxysteroid dehydrogenase (3\g=b\-HSD)activity of aged female rats (Shapiro & Leathem, 1971). Other studies show no age-related decline in 'resting ' plasma (Hess & Riegle, 1970) or adrenal (Sencar\x=req-\ Cupovic & Milkovic, 1976) corticosterone content in rats. Studies relating ageing and pituitary\p=n-\ adrenal function have also yielded apparently conflicting results. A reduced plasma corticosterone response to adrenocorticotrophin (ACTH) occurred in aged mice (Eleftheriou, 1974) and rats (Hess & Riegle, 1970), but plasma corticosterone levels after stress were similar in young and old rats (Sencar-Cupovic & Milkovic, 1976). Corticosteroid levels in the circu-lation, however, may inaccurately reflect adrenal function should alterations in steroid metabolism occur. To assess more directly adrenal function and sensitivity to ACTH with advancing age we report adrenal 3\g=b\-HSDactivities in young and aged mice with and without ACTH treatment. Female C57BL/6J mice (Jackson strain) reared in this laboratory were maintained and mate