By utilizing an antiserum which recognized the amino-terminal region of the amphibian peptide, physalaemin, it has been possible to isolate several cross-reacting peptides from rabbit stomach; these peptides have been designated physalaemin-like immunoreactive peptides (PHLIPs) PHLIP-8 has the following structure: less than Glu-Val-Asp-Gln-Ala; PHILIP-7 is identical to PHLIP-8 in the amino acid sequences 1-7. These peptides do not possess tachykinin properties characteristic of amphibian physalaemin or of Substance P; they appear to be degradation products of larger molecules which have recently been recovered from rabbit stomach tissue. Because several of the biological properties of the PHLIP precursors are similar to those of physalaemin, efforts are underway to purify these larger peptides. It is possible that the PHLIPs are ultimately derived from stomach glycoproteins, e.g., mucin. Since material which cross-reacts with physalaemin antiserum has been detected in central nervous system tissue, it is probable that such material is structurally more similar to the PHLIP precursors than to physalaemin; antisera will be obtained for PHLIP-8 and will be used to redetermine the content and distribution in the central nervous system of PHLIP cross-reacting materials.
