Responses of python gastrointestinal regulatory peptides to feeding

In the Burmese python (Python molurus), the rapid up-regulation of gastroin testinal (GI) function and morphology after feeding, and subsequent down-re gulation on completing digestion, are expected to be mediated by GI hormone s and neuropeptides. Hence, we examined postfeeding changes in plasma and t issue concentrations of 11 GI hormones and neuropeptides in the python. Cir culating levels of cholecystokinin (CCK), glucose-dependent insulinotropic peptide (GIP), glucagon, and neurotensin increase by respective factors of 25-, 6-, 6-, and 3.3-fold within 24 h after feeding. In digesting pythons, the regulatory peptides neurotensin, somatostatin, motilin, and vasoactive intestinal peptide occur largely in the stomach, GIP and glucagon in the pa ncreas, and CCK and substance P in the small intestine. Tissue concentratio ns of CCK, GIP, and neurotensin decline with feeding. Tissue distributions and molecular forms (as determined by gel-permeation chromatography) of man y python GI peptides are similar or identical to those of their mammalian c ounterparts. The postfeeding release of GI peptides from tissues, and their concurrent rise in plasma concentrations, suggests that they play a role i n regulating python-digestive responses. These large postfeeding responses, and similarities of peptide structure with mammals, make pythons an attrac tive model for studying GI peptides.