<i>IN VITRO</i>BIOASSAY FOR THE MELANOCYTE STIMULATING HORMONE¹

Abstract

In 1919 Atwell showed that extracts from mammalian pituitary glands darkened the skin of hypophysectomized tadpoles. Since then the active principle, considered a hormone, has been known as intermedin, melanophore dilating principle, melanophore hormone, etc., with reference to its source in the intermediate lobe of the pituitary gland or its site of action, the melanophores of amphibia. Because the term melanocyte (Fitzpatrick and Lerner, 1953, Gordon, 1953) recently was adopted as the name for the melanin forming cell in all animals, and because mammalian as well as amphibian melanocytes are affected by the pigment-cell activating principle of the pituitary gland, the latter has been designated as melanocyte stimulating hormone (MSH). Most of the early methods for determining MSH consisted of observing in vivo darkening of frogs or fish injected with the hormone. Recently Friedin, Fishbein, and Hisaw (1948) described an in vitro assay in which the darkening of isolated frog