Hormonal control of melanin synthesis in birds

Abstract

It is well known that interstitial cell-stimulating hormone (ICSH, also known as luteinizing hormone) and hormones with ICSH-like activity cause feathers in the weaver bird to become black. This action of these hormones involves the deposition of melanin in the feathers and results, at least in part, from increased activity of the enzyme tyrosinase. The increase in tyrosinase occurs under the same circumstances as the deposition of melanin in response to ICSH. The action of ICSH upon tyrosinase activity is not inhibited by doses of puromycin which inhibit protein biosynthesis in regenerating feathers and does not therefore appear to require synthesis of protein de novo. Estradiol causes neck feathers of the Brown Leghorn to assume a pinkish-brown color due to the presence of a pigment with the chemical properties of melanin. The action of estradiol involves increased tyrosinase activity. This response to estradiol appears to require synthesis of new protein since it is inhibited by puromycin in doses which inhibit protein biosynthesis in regenerating feathers. The action of the two hormones ICSH and estradiol in increasing tyrosinase activities in feathers of two species of bird appears therefore to involve different biochemical mechanisms.