Assay of prolactin in vertebrate pituitaries by its dispersion of xanthophore pigment in the teleost Gillichthys mirabilis

Publisher Website
Google Scholar
Abstract
A simple, rapid assay for prolactin is described using the pigment‐dispersing response of the xanthophores in the teleost Gillichthys mirabilis. The assay is highly specific for prolactin in lower vertebrates, but mammalian growth hormone (STH) also produces a response in the assay. The assay is sensitive, detecting 10−11 gm (dry weight) of a teleostean pituitary rostral lobe. Taxonomic specificity is high: 5 μg ovine prolactin is required for a similar effect. Activity in the agnathan pituitary was negligible. In elasmobranchs, teleosts and reptiles, activity was localized in the rostral pituitary region. Lung‐fish pituitary activity was low, resembling that in tetrapods. Comparison of pituitary xanthophore activity from the several vertebrate classes indicates an inverse relationship with pigeon cropsac activity, previously published, suggesting that the evolution of a single active site on the prolactin molecule could account for both activities.