IMMUNOCHEMICAL CHARACTERIZATION OF CHOLECYSTOKININ-LIKE PEPTIDES IN LAMPREY GUT AND BRAIN

We have used chromatographic techniques in conjunction with radioimmunoassay employing antisera with selective specificity for different regions of mammalian gastrin and cholecystokinin (CCK) to examine the properties of CCK-like peptides in lampreys. In brain and intestine of Lampetra tridentata and L. fluviatilis there were two factors which cross-reacted with antisera specific for the COOH terminus of mammalian gastrin or CCK. Antisera specific for the NH2 terminus of heptadecapeptide gastrin, for intact heptadecapeptide gastrin, and for caerulein failed to reveal immunoreactive components. The quantitative pattern of cross-reactivity of the lamprey factors in both brain and gut resembled, but was not identical to, that of COOH-terminal fragments of cholecystokinin. The principal component emerged from Sephadex and Bio-Gel gel filtration columns in a similar region to CCK-like peptides of 7-10 residues. A minor component appeared to be slightly smaller and less negatively charged. We conclude that the antigenic determinant in the COOH-terminal region of gastrin and CCK has been strongly conserved during evolution. The results also indicate that the distribution of CCK-like peptides in brain and gut was established relatively early in vertebrate evolution. © 1979.