Cyclic oscillations in melanin composition within hairs of baboons

The wild-type agouti-banding pattern for hair is well characterized in lowe r mammals such as mice. The switch between eumelanin and pheomelanin in ban ds in the hair results from the interaction of alpha-melanocyte stimulating hormone and agouti signal protein through the melanocortin 1 receptor on m elanocytes, However, such banding patterns have not been described to date in higher mammals. We now report such 'agouti'-banding patterns that occur in several subspecies of baboons, and characterize those hairs using chemic al and immunohistochemical methods. Hair and skin samples were obtained fro m the dorsa of adult male baboons of different subspecies (Papio cynocephal us hamadryas (PCH) and Papio cynocephalus anubis (PCA)), The hairs were exc ised with scissors into the gray and the white bands of the PCH subspecies and into the black and the yellow bands of the PCA subspecies, and were ana lyzed for total melanin, eumelanin, and pheomelanin by spectrophotometric a nd chemical methods. Hairs in the PCA subspecies oscillate between a eumela nic band (with high melanin content) and a pheomelanic band, while hairs in the PCH subspecies oscillate between a eumelanic band (with low melanin co ntent) and a non-pigmented band, Those chemical data are consistent with th e histological appearance of the hair bulbs stained by the Fontana-Masson t echnique. The difference in the melanin content between PCH and PCA subspec ies is most likely related to tyrosinase levels, as suggested by the presen ce of unpigmented muzzle in the PCH subspecies compared with the black muzz le in the PCA subspecies.