Characterization of the increased estrogen synthesis in skin fibroblasts from the Sebright bantam

We have utilized the Sebright bantam chicken as a model system to explore the regulation of estrogen formation in peripheral tissues. As the result of a gene mutation, Sebright males develop a female feathering pattern associated with an increase in estrogen synthesis in skin and in fibroblasts cultured from skin. To provide insight into the mechanisms by which estrogen synthesis is increased we examined several parameters of the aromatase reaction in homogenates from control ovaries, Sebright ovaries and fibroblasts grown from Sebright skin: the pH optima; the apparent Km's for testosterone, 19-nortestosterone, androstenedione, 16-hydroxyandrostenedione, and NADPH; the apparent Ki's for 4-hydroxyandrostenedione, aminoglutethimide, dehydroepiandrosterone, and 19-hydroxytestosterone; and the inactivation of the reaction by heating. No qualitative differences were identified in the enzyme from Sebright and control birds.