Regional circulatory effects of pancreatic glucagon.
1. The effects of close intra-arterial injections and infusions of glucagon on blood flow in the femoral, hepatic and superior mesenteric arteries of anaesthetized cats were studied using non-cannulating electromagnetic flow probes.2. Glucagon dilated the mesenteric vasculature. The threshold dose for rapid injections was less than 1 mug and maximal changes were produced by 10-20 mug. The dilatation began within a few seconds of injection and was unaffected by prior denervation or by pre-treatment with propranolol or atropine.3. Close intra-arterial glucagon increased the resistance of the hepatic arterial bed but had no effect on femoral vascular resistance. Intravenous glucagon failed to alter renal blood flow.4. Glucagon is therefore a potent vasoactive substance with its effect wholly or predominantly confined to the splanchnic area.5. It has been suggested that the cardiac effects of glucagon and isoprenaline resemble each other because both compounds act on the beta-adrenoceptor mechanism. The different regional vascular effects of glucagon and isoprenaline suggest that glucagon vasodilatation may not be mediated via beta-adrenoceptors.