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Heparin-releasable liver-lipase like activity was studied in adrenals of intact, gonadectomized and gonadectomized-testosterone or estradiol replaced rats. Besides acid lipase, rat adrenals contain a neutral lipase activity. From both male and female adrenals about 70% of this activity is extractable by heparin containing medium. Activity of this lipase in 8000 g supernatant was higher in female than male adrenals. Orchiectomy of 12 weeks duration increased neutral lipase activity in rat adrenal, an effect reversed to normal level by testosterone replacement. On the other hand ovariectomy had no effect while estradiol replacement resulted in an increased activity of the neutral lipase of rat adrenal gland. The results showed a distinct sex-difference in heparin-releasable liver-lipase like activity of rat adrenals which depends on the inhibitory action of testosterone on the enzyme activity.

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In order to explain the disappearance of depot fat in rats fed on a diet containing 50% by weight of extremely hydrogenated vegetable fat, experiments were performed in which the diet inhibiting lipogenesis was enriched with biotin. Biotin was effective in maintaining normal adipose tissue stores. The dermal essential fatty acid deficiency syndrome which occurred in this dietary group was prevented by the administration of linoleic acid. Cecal contents of rats kept on diets with hydrogenated fat were analyzed for biotin concentration and showed depressed intestinal synthesis of this vitamin by the bacterial flora. These data suggest that the inhibited lipogenesis in animals fed extremely saturated fat is the result of essential fatty acid deficiency and thereby of a reduced synthesis (and increased utilization) of biotin required as coenzyme of fatty acid synthesis in the nonmitochondrial system of lipogenesis.