Abstract
Adrenocorticotropic extracts† were tested in normal 21-day-old male rats and in hypophysectomized rats. The amount of adrenocorticotropic hormone necessary to cause an increase of 50% over the adrenal weight of controls when injected into 21-day-old male rats in 3 doses over a period of 3 clays was defined as one normal rat unit. A total dose of 20 mg. was usually found to be adrnal to one unit.
The injections of large amounts of beef brain (1000 mg.) produced no significant change in adrenal weights of normal 21-day-old male rats. Adrenocorticotropic preparations from beef anterior pituitaries showed the same activity as adrenocorticotropic preparations from whole sheep pituitaries, indicating that posterior lobe substances were not causing the hypertrophy of the adrenal cortex in the normal male rats.
Male rats between 40 and 50 days old were hypophysectomized,† and at least 30 days were allowed for atrophy of the adrenals before injections were begun. The completeness of the operation was checked by examination of the sella turcica under dissecting binoculars. Table I shows the effect of adrenocorticotropic extracts in hypophysectomized rats.
From the results obtained in hypophysectomized rats, it can be seen that the adrenocorticotropic preparations contained no growth hormone at the level tested. The thyroids showed no histological evidence of stimulation.
Adrenocorticotropic extracts when injected subcutaneously into squabs for 4 days showed no stimulation of the thyroids or of the testes. The crop glands were stimulated.
Adrenocorticotropic and mammotropic fractions from the same extract were compared at various levels for their adrenocorticotropic potencies in normal 21-day-old male rats. The results are given in Graph 1.
The adrenal cortices of nornial inimature rats in jectecl with aclrenocorticotropic hormones% (Fig. 2) differ niarkedly from the untreated controls (Fig. 1). There is an increased fat content throughout the whole adrenal cortex. In untreated controls there is an intermediate zone between the glonierulosa and the fasciculata in which there is very little or no fat.
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