GROWTH OF SECONDARY HAIR-FOLLICLES OF THE CASHMERE GOAT IN-VITRO AND THEIR RESPONSE TO PROLACTIN AND MELATONIN

The isolation and viability in vitro of anagen secondary hair follicle s of the Cashmere goat were studied. Isolated hair follicles were used to determine the effects on hair shaft elongation, of prolactin and m elatonin, hormones considered to influence hair follicle growth and ac tivity in vivo. Intact hair follicles were isolated from the dermal la yer of the skin singly or in groups using watchmakers' forceps under a dissecting microscope. The isolated follicles were maintained floatin g in Williams E medium. The medium was supplemented with 1 of 6 concen trations of ovine prolactin (0, 50, 200, 400, 800 and 4000 mu g/l) for the culture of hair follicles isolated during July and August, and wi th 1 of 5 concentrations of melatonin (0, 50, 150, 300, 600 ng/l) for the culture of hair follicles isolated during September and October. T here was clear evidence of DNA synthesis, observed by autoradiography, in matrix cells of freshly isolated follicles incubated for 6 h in th e presence of [methyl-H-3]-thymidine. Similar measurements after 96 h of maintenance indicated a marked reduction in the incorporation of [m ethyl-H-3]-thymidine in matrix cells of the follicles studied. Prolact in and melatonin were shown to have a stimulating effect on hair shaft elongation of secondary follicles during 24 h periods of measurement and cumulatively over 120 h. Maximum hair follicle growth was observed in follicles exposed to 400 mu g/l of prolactin and follicles exposed to 300 ng/l of melatonin. The number of follicles remaining viable du ring each 24 h measuring period was not affected by prolactin, but was significantly reduced by melatonin treatment after 96 h of maintenanc e. Hair follicle growth was significantly greater in July/August than September/October. The results for the in vitro method used suggest th at prolactin and melatonin may act directly on the Cashmere secondary hair follicle to stimulate elongation of the hair shaft and that melat onin may reduce the viability of follicles after 96 h incubation. The results are discussed in the context of the possible involvement of pr olactin and melatonin in the seasonal control of the hair growth cycle in vivo.