title: Size heterogeneity of rat pituitary prolactin.
abstract: The occurrence of multiple forms of rat prolactin with different molecular weights (size heterogeneity) was studied with anterior pituitary extracts, purified rat prolactin and 125I-labelled rat prolactin. In each case, three main forms of the hormone were detected by gel filtration on Sephadex G-100: a major one (80--90%) corresponding to monomeric prolactin (mol.wt. 22000--25000), a peak (8--20%) that could be a dimer (mol.wt. 45000--50000) and a small quantity (1--5%) of a component of much greater molecular weight. On freezing and thawing of 125I-labelled rat prolactin, there was little interconversion of monomer and 'dimer' peaks, but both were converted substantially to very high-molecular-weight material. All three peaks of 125I-labelled rat prolactin could be precipitated by anti-(rat prolactin) serum and all three gave similar patterns of radioactive peptides after digestion with chymotrypsin followed by high-voltage paper electrophoresis. On sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, the monomer peak of 125I-labelled prolactin migrated as a single component of mol.wt. 22000, the very high-molecular-weight peak largely dissociated to a component running in the same position as the monomer, and the 'dimer' peak migrated partly as a component of mol.wt. 45000 and partly as a component migrating with monomeric prolactin. No treatment was found that could dissociate the 'dimer' peak completely to monomeric prolactin.
mesh_terms: D000818:Animals; D011232:Chemical Precipitation; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D005615:Freezing; D013006:Growth Hormone; D007457:Iodine Radioisotopes; D008970:Molecular Weight; D010903:Pituitary Gland, Anterior / Q000032:analysis*; D011388:Prolactin / Q000276:immunology; D051381:Rats
chemical_list: D007457:Iodine Radioisotopes; D011388:Prolactin; D013006:Growth Hormone