An improved method is described for the assay of the enzymic activity of cholesterol side-chain cleavage in rat adrenal glands. The method makes use of double isotope labeling and can be conveniently applied to smaller tissue samples than has been possible hitherto. With this improved technique, a study of the cholesterol side-chain cleavage activity of the adrenals of rats of various ages, from 1 to 46 days, has been undertaken and the results are reported. The enzyme activity is relatively high in the adrenal gland of the 1-day-old rat, but falls during the first 6 postnatal days, remains low until about the 12th postnatal day, then rises to a higher level by about the 25th day. This developmental pattern correlates closely with that which has been reported for the responsiveness of the adrenal of the neonatal rat to stress. Repeated injections of ACTH (adrenocorticotropic hormone) for 8 days prevent the decline of cleavage activity in the adrenal of the newborn. Treatment with ACTH for 2 days is not long enough to raise thelevel of cleavage activity, but is sufficient to stimulate the over-all growth of the gland. Inolder, prepubertal female rats (intact or hypophysectomized) the effects of injected ACTH are in the same sequence: First the mass of the glands increases without a corresponding increase in the cleavage activity. After several days of continued ACTH treatment, the concentration of the cleavage activity is restored. (Endocrinology85: 500, 1969)
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Charles H. Doering (1969) studied this question.