Positive inotropic effect of carcinine in the isolated perfused guinea pig heart

Carcinine (beta-alanylhistamine) is a recently discovered compound that is present in the hearts of several mammalian species, including man. Although the function of carcinine is unknown, its structural similarity to histamine, a compound known to have profound effects on the mammalian heart, and to carnosine (beta-alanylhistidine), a compound which we have previously shown to serve as a histamine source, led to the hypothesis that carcinine may play a role in mammalian cardiac physiology. We therefore administered several doses of carcinine (10, 25, 50, 75, and 100 micrograms) to isolated, perfused guinea pig hearts in a Langendorff apparatus. Carcinine exerted a dose-dependent positive inotropic effect, similar to that of histamine. Comparable doses of carnosine yielded no measurable change in contractility. We conclude that carcinine appears to be a positive inotrope in the mammalian heart, and may play a role in cardiac physiology via its metabolic link to histamine.