EFFECTS OF ADMINISTRATION OF TESTOSTERONE, DIHYDROTESTOSTERONE, ESTROGEN AND FADROZOLE, AN AROMATASE INHIBITOR, ON SEX SKIN COLOR IN INTACTMALE RHESUS MACAQUES

For defining the mechanism of control of sex skin colour in male rhesu s macaques (Macaca mulatta) by hormones, a spectrocolorimeter was used to monitor skin redness after administration of testosterone, dihydro testosterone (a non-aromatizable androgen), oestradiol or fadrozole (a n aromatase inhibitor that blocks the conversion of testosterone to oe strogen). Skin blood flow was measured by laser doppler. Eight 9-14 kg , 5-9 year old intact male rhesus macaques were given hormone, fadrozo le or vehicle treatments in a cross-over experimental design. Baseline blood flow and colour measurements were taken in four paired tattoo d efined areas on the back and legs of each animal (one pair in non-sex skin, three pairs in sex skin). Colour and blood flow measurements wer e taken 3-4 days after the first dose and, thereafter, once a week for 3-6 weeks. Measurements taken after treatments were compared with bas eline and intra-animal comparisons were made between treatment and veh icle for each animal. In all animals after administration of 4 mg test osterone kg(-1) (long-acting), redness in the sex skin areas increased (P = 0.032) by day 3 and returned to baseline values by day 7. Admini stration of 1 mg oestradiol kg(-1) day(-1) for 4 days caused increased redness in all animals (P = 0.007) similar in magnitude to that cause d by testosterone. Administration of 0.1 mg dihydrotestosterone kg(-1) day(-1) for 4 days resulted in a nonsignificant decrease in redness ( P = 0.09) on days 3-7. Treatment with fadrozole (0.25-0.5 mg kg(-1) da y(-1)) for 3 weeks caused sex skin to become significantly less red du ring treatment (P=0.014). There was no significant change in redness i n non-sex skin areas during any treatment. Sex skin blood now increase d in animals treated with testosterone, correlating with increased red ness (R = 0.906), while blood flow in non-sex skin was unchanged. Incr eased redness after treatment with testosterone and oestrogen, no chan ge in redness with treatment with dihydrotestosterone and a decrease i n redness after treatment with fadrozole support the conclusion that o estrogen controls sex skin redness, and testosterone acts indirectly t hrough conversion to oestrogen to cause increased sex skin redness in male rhesus macaques.