Prolactin (PRL) is a single-chain polypeptide hormone that elicits a wide variety of physiologial responses in vertebrates; in mammals these include growth and development of the mammary gland and lactation. In recent years it has also become evident that PRL exerts marked effects on the immune system and several types of immune cells possess PRL receptors: for example the hormone is a powerful, lactogen receptor-mediated mitogen for rat Nb2 pre-T lymphoma cells. PRL is considered to be a member of a hormone famioly which includes growth hormone and placental lactogen, and these hormones are believed to share a similar three-dimensional structure. There is considerable interest in determining which regions of these polypeptides are functionally important. The principal objective of the proposed research is to define the amino acid residues in PRL which are responsible for its biological activities, particlarly its mitogenic action on Nb2 cells. The availability of these cells makes possible a detailed structure- function analysis of PRL with regard to its action as a growth- stimulating factor. The Nb2 cell will be used as tools in these studies of how the structure of PRL affects its biological activity. %%% The study of prolactin and growth hormone has wide application, since these hormones regulate numerous physiological processes for normal and disease states in humans, and for the reproduction, development, and productivity of economically valuable livestock. Althugh these studies are basis, by concentrating on bovine prolactin and growth hormone, and on the bovine mammary gland prolactin receptor, the //
