Effect of the Melanocyte Stimulating Hormone of the Pituitary on Melanocytes and Melanin in the Skin of Guinea-Pigs

Abstract

1. The effect of beta melanocyte stimulating hormone (\g=b\-M.S.H.) extracted from the posterior pituitary of the hog, on the melanocytes and melanin in the skin of the ear, anterior abdominal wall, areola and sole of foot has been studied in pure black and pure red intact male and ovariectomized female guinea-pigs. The hormone was injected subcutaneously twice daily 5 days/ week for 1 month.2. Apart from a slight increase in the pigmentation of the skin of the anterior abdominal wall and areola of one male guinea-pig, no obvious changes were noted microscopically.3. Histological investigation showed that the hormone caused an increase in the length, width and complexity of the dendritic processes and that this was accompanied by an increase in the amount of melanin present within the processes. In the skin of the anterior abdominal wall numbers of melanocytes were significantly raised and the amount of free melanin was increased. In many of the animals the amount of melanin present within the cell bodies of the melanocytes was increased in all the skin regions and in some of these this was associated with an increase in size of the cell body.4. The hormone produced its greatest effect on the melanocytes in males.

Sensitive Method for the Bioassay of Melanocyte Stimulating Hormone in Human Saliva

“…We were able to establish a standard curve for the activity of MSH (Fig 4) (2) /delta (1)], the standard curve was approximately linear in the range of darkening ratios produced by saliva samples. By use of this standard curve with known values of MSH, it was possible to determine relative MSH-like activity in samples of human saliva.…”

“…After one-hour exposure of the frog skin to the human saliva, a fourth reflectance reading was made. The difference between the third and fourth readings was labeled as delta (2). The human saliva used in these experiments had been previouslv collected from normal, healthy volunteers who had chewed on rubber bands to stimulate the flow of saliva.…”

The Effect of Corticotrophin on the Activity of Mammalian Epidermal Melanocytes

“…Previous work on guinea-pigs (Snell, 1962(Snell, , 1963 showed that alpha and beta MSH cause an increase in the length, width and complexity of the dendritic pro¬ cesses of the epidermal melanocytes and increase the amount of melanin present both inside and outside the processes. These results explained the mechanism underlying the darkening of the skin which occurs in man after the administration of these hormones (Lerner & McGuire, 1961).…”

“…At the end of the hormone treatment a second specimen of skin was taken from the anterior abdominal wall from an area adjacent to that taken previously and the left areola was excised. After removing excess subcutaneous fat and part of the dermis under the dissecting microscope, each skin specimen was processed as described previously (Snell, 1962). The greater part of each skin sheet was then mounted in Depex, the remainder was embedded in paraffin and vertical sections, 6 ¡i thick, were cut.…”

Excerpts from the Pharmacology of Hormones and Related Substances

“…Snell (12) has studied the influence of pig ,8-MSH on the melanocytes and melanin in the skin of twelve adult normal male and castrate female guinea pigs. Subcu taneous administration of the hormone, roughly 800 IU for a month in each animal, provoked in only one male guinea pig a slight increase in the pigmen tation of the skin of the anterior abdominal wall and areola.…”