ENDOCRINE FACTORS AFFECTING CELL REPLACEMENT AND CELL LOSS IN THE EPIDERMIS AND SEBACEOUS GLANDS OF THE FEMALE ALBINO RAT

Abstract

SUMMARY: 1. Hypophysectomy and adrenalectomy in female albino rats aged 9 months were followed by an enlargement of the sebaceous glands and a thickening of the stratum germinativum plus stratum granulosum in the skin of the back. In similar rats aged 5 months hypophysectomy produced a very significant increase in epidermal thickness, but the increase in the mean volume of the sebaceous glands was not statistically significant. 2. In rats aged 5 months hypophysectomy appeared to increase the incidence of mitoses in both tissues, as measured 5 hr after the injection of colchicine. In rats aged 9 months these increases were less marked in the sebaceous glands and insignificant in the stratum germinativum. 3. Implantation of oestradiol/cholesterol for 3–4 weeks caused a marked reduction in size of the sebaceous glands in intact, in hypophysectomized, and in adrenalectomized rats. Epidermal thickness remained unaffected in intact adult rats, but was reduced in hypophysectomized or adrenalectomized rats. 4. The incidence of mitoses in the sebaceous glands and stratum germinativum was not affected 3–4 weeks after the implantation of oestradiol in intact, in hypophysectomized, and in adrenalectomized rats. 5. Spaying had no significant effect on sebaceous gland size, epidermal thickness, or incidence of mitoses. 6. The following main conclusions are suggested by the results: (a) The normal breakdown of sebaceous cells, epidermal keratinization and subsequent cell loss in the skin of the back of the rat are delayed by interference with the pituitary-adrenal system. (b) Oestradiol accelerates the breakdown processes even in the absence of the pituitary and adrenal glands. (c) In the adult female rat mitosis in the epidermis and sebaceous glands neither requires nor is greatly affected by the presence of oestradiol. (d) In the absence of the pituitary the incidence of mitoses in the epidermis and sebaceous glands may be increased; it is possible therefore that a pituitary or adrenal hormone may inhibit mitosis.