Effects of testosterone and alpha-melanocyte-stimulating hormone on preputial-gland (sebaceous) activity.

The preputial glands in the rat are large modified sebaceous glands, which are believed to be the source of a sex pheromone (Gawienowski et al., 1975). Their main secretory product is neutral lipid, which contains an unusually high proportion of squalene as well as wax esters and glyceryl ether lipids (Nicolaides, 1965; Helmy & Hack, 1967). Like cutaneous sebaceous glands their secretion is holocrine in nature, consisting of autolysed whole cells, and the secretory activity of the gland depends both on the lipogenic capacity of individual cells and on the rate of cell proliferation and turnover. Preputial-gland size is under endocrine control from the gonads and pituitary (Thody & Shuster, 1975). In a holocrine system, gland size by itself is not asufficient indicator of activity, and we have therefore studied the lipogenic capacity of the gland by measuring the incorporation of [U-14C]glucose into lipids. Here we report the effects of hypophysectomy, castration, posterior hypophysectomy and replacement with testosterone or a-melanocyte-stimulating hormone. Adul t male rats were castrated, hypophysectomized or posterior-h ypophysect omized at 9-1 1 weeks of age. Hormone injections were commenced 3-4 weeks later. Testosterone propionate was given subcutaneously in isopropyl myristate and a-melanocyte-stimulating hormone was given subcutaneously twice daily in 0.9 % NaCI. Control groups received injections of vehicle alone. At the end of the injection period the animals were killed and the preputial glands were removed and weighed after expulsion of sebum by gentle pressure. The minced tissue was incubated for 3 h at 37°C in Krebs-Ringer bicarbonate buffer containing antibiotics and 2m~-~'~C]glucose (5 mCi/mmol) under Oz+COz (95 : 5). After incubation total lipids were extracted and separated into classes by one-dimensional t.1.c. on silicic acid. Details of this method have been reported (Cooper et al., 1974; Thody et al., 1976). Removal of the pituitary decreased preputial-gland weight and lipogenic activity (Table 1). The labelling of ail lipid classes was decreased, but squalene and the wax monoesterlsterol ester fraction were affected to a much greater extent than other lipids; thus after hypophysectomy these classes represented a smaller proportion of the total labelled lipid (Table 2). Castration also decreased preputial-gland weight and lipogenic activity, but to a smaller extent than did hypophysectomy (Table 1). Replacement with testosterone propionate (0.2mg/100g body wt. per day for 2 weeks) in castrated animals restored gland weight and lipogenesis to normal (Table 1). The failure of castration to reproduce the full effect of hypophysectomy implies the existence of a pituitary factor, other than gonadotrophins, controlling preputial-gland size and activity. This factor could be the intermediate lobe hormone, a-melanocytestimulating hormone. Removal of the neurointermediate lobe of the pituitary, although leaving the anterior lobe functional as judged by adrenal and testes weight, reduced preputial-gland weight and lipogenesis (Table 1). In these posterior-hypophysectomized animals, treatment with a-melanocyte-stimulating hormone (3Opg/lOOg body wt. per day for 10 days) restored gland weight and activity to normal (Table 1). In order to compare the effects of testosterone and a-melanocyte-stimulating hormone, hypophysectomized rats were treated with testosterone alone, a-melanocyte-stimulating hormone alone, or the two hormones together. The results of this experiment are shown in Table 2. a-Melanocyte-stimulating hormone (lOOpg/lOOg bodt wt. per day for 2 weeks) given to completely hypophysectomized rats had no significant action on preputial-gland weight or on I4C incorporation into total lipids, even though a smaller dose of a-melanocyte-stimulating hormone was completely effective in the presence of the