Distinction between cholecystokinin-like and gastrin-like biological activities extracted from gastrointestinal tissues of some lower vertebrates

Abstract

A technique which allows differentiation between cholecystokinin-like (CCK-like) and gastrin-like biological activity is described. Contractions of two strips of digestive smooth muscle with differing CCK/gastrin specificities, mounted in parallel and superfused in the tissue-oil interface in an oil bath, are measured. Such laminar flow superfusion in oil is demonstrated to be a more sensitive technique for detecting CCK and gastrin than the simple muscle bath preparation in which the muscle strip is bathed in physiological salt solution. In such a parallel laminar flow superfusion, gallbladder muscle from the guinea pig is more sensitive to porcine CCK than is guinea pig antral muscle, and the opposite potency order of gallbladder and antrum is seen for porcine gastrin. This differential order of threshold potencies of gallbladder and antral muscle is exploited to distinguish CCK-like and gastrin-like factors in crude extracts of gastrointestinal tissues from several vertebrate species. Crude stomach extracts prepared from rat, frog ( Rana berlandieri), and coho salmon ( Oncorhynchus kisutch) exhibited a gastrin-like pattern of biological activity. However, a crude extract prepared from dogfish ( Squalus acanthias) stomachs exhibited a CCK-like pattern of biological activity. Crude intestinal extracts prepared from rat, frog, coho salmon, dogfish, and hagfish ( Eptatretus stouti) were CCK-like in their pattern of biological activity. It is suggested that a CCK-like factor or factors preceded gastrin-like factors in vertebrate evolution and that the gastrins may have evolved from a CCK-like factor at the level of the divergence of chondrichthyeans and osteichthyeans.