Abstract
Gila monster venom (1–300 μg/ml) is shown to inhibit completely the binding of [ 125I]VIP to human and rat intestinal epithelial cell membranes. In both models, the venom inhibits [ 125I]VIP binding and stimulates adenylate cyclase with a maximal efficiency that is similar to that of VIP and a potency that is 10 000–50 000 times lower than that of the peptide, on a weight basis. At maximal doses, VIP and Gila monster venom do not exert an additive effect on adenylate cyclase, suggesting that the activation of the enzyme by the venom occurs through VIP receptors. As is the case for VIP, adenylate cyclase activation by Gila monster venom requires the presence of GTP in the incubation medium. Finally, no VIP-like immunoreactivity was detected in the venom using an antiserum raised against mammalian VIP. All these data suggest the presence in the venom of the Gila monster, of a new substance which behaves as a VIP agonist in human as well as rat intestine.
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