Preliminary Characterization of the Pituitary Melanocyte Stimulating Hormones of Several Vertebrate Species

A survey of pituitaries of several vertebrate species was carried out in an effort to determine whether they contained melanocyte stimulating hormones and, if so, whether they were identical with those which have previously been structurally characterized. All ten of the species studied possessed biologic melanocyte stimulating substances. In only two species (pig and beef) was it possible to account for a majority of the biologic activity in terms of known hormones, using a combination of bioassays for MSH and ACTH and radioimmunoassays for α-MSH, β-MSH and ACTH. In eight species (flounder, frog, iguana, chicken, guinea pig, mouse, rat and rabbit) there was an excess of biologic MSH activity that could not be accounted for by a summation of ACTH, α-MSH, and β- MSH. It is concluded that, in these species, the structures of the major melanocyte stimulating hormones are different from any that have been characterized previously. (Endocrinology90: 249, 1972)