THE EFFECTS OF PROLONGED ADMINISTRATION OF CORTISOL ON THE SKIN OF SHEEP ON DIFFERENT PLANES OF NUTRITION

Abstract

SUMMARY The effects of prolonged administration of cortisol on epithelial and dermal tissues were examined in three groups of non-pregnant ewes with different food intakes. The changes observed depended on the degree of increase in plasma cortisol and in some instances on the amount of food eaten. Successive increases in plasma cortisol up to about 3 μg/100 ml progressively inhibited the tissues in the skin of sheep on restricted food intakes, but not those in the skin of sheep which increased their intakes. In the latter, a slight increase in plasma cortisol to about 1 μg/100 ml stimulated wool production and fibre-length growth rate. Moderate increase to about 2 μg/100 ml produced temporary enlargement of sweat glands, dilatation of capillaries and an increase in the number of dermal mast cells. Regardless of the amount of food eaten, retrogression of all epithelial and dermal components was maximal when plasma cortisol remained above about 3 μg/100 ml. Follicle inactivation and cessation of fibre-growth occurred with the formation of brush-ends on the fibres. The retrogression of the tissues occurred in spite of increased blood glucose concentrations, indicating that cortisol depressed the utilization of glucose by the skin. Keratinization of the epidermis was altered and was possibly hastened. The rates of recovery of the different tissues after cessation of cortisol administration were variable. Follicle regeneration and commencement of fibre regrowth were the slowest. The epidermis of the sheep on restricted food intake showed an unusual thickening. Cortisol acetate applied topically to the skin of other sheep produced changes consistent with those induced by injected cortisol.