Immunological studies with rat pituitary growth hormone (RGH) II. Comparative immunochemical investigation of GH from representatives of various vertebrate classes with monkey antiserum to RGH

Abstract

The immunochemical relatedness of GH in pituitary extracts from various vertebrate species has been studied by means of precipitin reactions in agar and by radio-immunoassay. Extracts were prepared from the pituitaries of animals representing most of the vertebrate classes. The results which were based on the use of monkey antiserum to RGH, indicated that GH from mammalian species must share a relatively large number of common antigenic determinants and that the greater the phylogenetic distance from the mammal, the fewer such determinants were shared by the GH molecule from any particular species. The agar diffusion studies based on reactions of identity and reactions of partial identity and the quantitative results of immunochemical relatedness based on radioimmunoassays, revealed a separation of GHs from the various vertebrate species into a series of immunochemical categories which closely corresponded to their respective phylogenetic classes based largely upon morphological considerations. Bioassays were also performed to determine the capacity of GH in the pituitary extracts from representativees of the various vertebrate classes to stimulate growth by means of the tibia test in hypophysectomized rats. It was concluded on the basis of the current series of investigations that theresults of the immunochemical approach have shown a general correlation with evolutionary development and was more reliable in this regard than the biological approach.