Effect of adrenocorticotropin on the concentration of triglyceride in the adrenal gland of the hypophysectomized rat.

The concentration of triglyceride in the adrenal gland, measured by the method of Van Handel and Zilversmit, was found to be 2.2-3.2 mg/100 mg fresh tissue in the normal rat; this value increased to 3.5-4.8 mg/100 mg tissue 24-48 hr after hypophysectomy. Injection of 0.1-10 U of adrenocorticotropin in the rat 24-48 hr after hypophysectomy caused a 20-45% reduction in adrenal triglyceride concentration. This effect was apparent 3 hr after injection and persisted for at least 6 hr. {Endocrinology 78:1087, 1966) H observations first revealed that the adrenal cortex contains an abundant quantity of lipid, which is depleted by a single injection of adrenocorticotropin (ACTH) or by a variety of acute noxious stimuli (1). The chemical nature of the cortical lipid thus depleted has been the object of numerous studies, which agree that adrenal cholesterol esters are reduced by an adrenocorticotropic stimulus and that adrenal phospholipid concentration remains unchanged (1-4). Adrenal triglyceride content, however, has been reported increased (4), unchanged (3), or decreased (2) in animals subjected to acute stressful stimuli; these discordant data were obtained with indirect methods for calculating triglyceride content, since a specific analytic method for this lipid was not available until recently. The introduction by Van Handel and Zilversmit (5) of a direct method for determining triglyceride, and recognition of the influence of ACTH on the triglyceride metabolism of the fat cell, have led us to re-examine the possible effect of ACTH on the triglyceride content of the rat's adrenal gland. Materials and Methods Intact and hypophysectomized male Wistar rats weighing 250-260 g were obtained from Charles River Laboratories and were fed Purina Laboratory Checkers ad lib. The experiments were begun 2448 hr after hypophysectomy. Intact and hypophysectomized rats were injected subcutaneously with 0.5 ml normal saline or with 0.1-10 U clinical porcine ACTH (Wilson Laboratories) in a volume of 0.5 ml. At stated periods thereafter, the animals were killed by cervical fracture, the adrenal glands Received December 10,1965. Supported by USPHS Grants AM-06056, HE05741 and HE-00052, and by Grant U-1562 from the Health Research Council of New York City. 1 Career Scientist of the Health Research Council of New York City under Contract 1-118. were dissected free of extraneous tissue under a dissecting microscope, weighed and homogenized in chloroform/methanol 2 :1 (20 ml of solvent/pair of adrenals). The chloroform /methanol extract was washed according to Folch et al. (6) and then was analyzed for triglyceride by the method of Van Handel and Zilversmit (6), and for total cholesterol by the method of Abell et al. (7). Results The triglyceride concentration in the adrenal glands of normal rats ranged between 2.2 and 3.2 mg/100 mg fresh tissue, while the concentration in the adrenals of hypophysectomized rats (not treated with ACTH) ranged between 3.5 and 4.8 mg/100 mg tissue; the difference between these 2 groups was statistically significant (p <.025) in each of 3 experiments (Table 1). Injection of 10 U ACTH in the hypophysectomized rat caused a statistically significant (p <.01) reduction in adrenal triglyceride concentration 6 hr later; this decrease ranged between 33 and 44% of the preinjection concentration (Expt. 1, 2, 3, Table 1). The magnitude of the reduction in triglyceride concentration was proportional to the dose of ACTH in the range 0.1-10 U of hormone (Expt. 3, Table 1); following 0.1 U, however, the triglyceride decrease was of doubtful statistical significance. The depletion of adrenal triglyceride produced by 0.1-10 U of ACTH was associated with a parallel decline in adrenal cholesterol content (Expt. 3, Table 1), as originally described by Sayers and colleagues (1). The reduction in adrenal triglyceride following injection of 10 U ACTH was apparent at 3 hr and persisted for at least 6 hr (Table 2). Discussion These data demonstrate that ACTH reduces the concentration not only of cholesterol, but also of triglyceride, in the adrenal gland of the hypophysectomized rat.