EFFECT OF THE ALPHA MELANOCYTE STIMULATING HORMONE OF THE PITUITARY ON MAMMALIAN EPIDERMAL MELANOCYTES

[摘要] The effect of alpha melanocyte stimulating hormones (MSH) on the melanocytes and melanin in the skin of the anterior abdominal wall and areola has been studied in pure black and pure red intact male and ovariectomized female guinea pigs. The hormone was injected subcutaneously once daily, 5 days/week for 1 month. Naked eye examination at the end of the hormone treatment showed a slight increase in the amount of pigmentation in both skin areas. Histological examination in the male showed that the hormone caused in the anterior abdominal wall skin an increase in the length, width and complexity of the dendritic processes of the melanocytes and an increase in the amount of free melanin. In the majority of the animals the amount of melanin within the dendrites was also increased and the amount of melanin within the cell bodies was decreased. In the areolar skin a great decrease in the amount of melanin within the cell bodies of the melanocytes was seen and an increase in the amount of free melanin occurred. In the female, similar histological findings were recorded, but in the areola practically no changes occurred. It appears likely that mammalian epidermal melanocytes react to alpha MSH in a similar manner to amphibian dermal melanocytes.