Isolation and amino acid compositions of four somatostatin-like substances in chicken hypothalamic extract.

Four peptides having SRIF-like bioactivity when assayed by a rat anterior pituitary cell culture system have been isolated from chicken hypothalamic extracts. These four peptides have been purified from 2,000-5,000 chicken hypothalami in a yield of 2.2 nmol to 16 nmol. The isolated SRIFs have been characterized by amino acid analysis. One consists of 28 amino acids which are identical with mammalian SRIF-28 except that one Met residue is replaced by a Leu residue. Three other SRIF-like substances with low mol wt have also been isolated in a pure state. One is identical with mammalian SRIF-14, as judged by chromatographic comparison on HPLC and its amino acid composition as well as the specific bioactivity on rat pituitary cells. The amino acid composition and specific bioactivity of another one is identical with that of mammalian SRIF-14, but it is different from mammalian SRIF-14 in its elution position on HPLC. The third SRIF-like substance consists of 16 amino acids and is less potent than mammalian SRIF-14. It is concluded that several SRIF-like peptides exist and that SRIF-28, with one amino acid substitution from Met to Leu, and SRIF-14, identical with the mammalian one, are the major components in chicken hypothalamus.