Three growth hormone- and two prolactin-related novel peptides of Mr 13,000-18,000 identified in the anterior pituitary.

Electrophoretic analysis of murine anterior pituitary extract revealed five major proteins of Mr 13,000-18,000 (designated P13, P14, P16, P17, and P18 according to Mr), three of which, P16, P17, and P18, were markedly influenced by estradiol benzoate and perphenazine in a manner similar to that of growth hormone, and two, P13 and P14, to that of prolactin. Tyrosine peptide mapping showed partial resemblance of fingerprints for P16 and P17 (and possibly P18) to those for growth hormone, and of P13 and P14 to those for prolactin. Both P14 and P18 bound to Concanavalin A. None of the peptides crossreacted with antibodies to growth hormone or prolactin. The concentrations of P13 and P14 in pituitaries from lactating rats and in a prolactinoma were distinctly higher than normal. All five peptides were secreted into the medium during the in vitro incubation. These results suggest that P16, P17 and P18 are growth hormone- and P13 and P14 prolactin-related secretory proteins of the pituitary.