A study of the acute and chronic cardiovascular effects of glucagon in the dog

Abstract

Studies were performed on dogs to clarify the acute effects of glucagon on selected cardiovascular and electrophysiological parameters, and to assess the chronic effect of the hormone on heart rate. The experiments were divided into three parts: (1) effects of intravenous glucagon administration on several cardiovascular indices, (2) effect of intravenous glucagon injection on atrial refractory period (ARP), A-V nodal functional refractory period (AVFRP), and ventricular refractory period (VRP), and (3) effect of repetitive, intramuscular injections of glucagon on heart rate and plasma glucose. The acute cardiovascular effects of glucagon were assessed in anesthetized dogs, in which elastomeric aortic and pulmonary arterial catheters had been implanted surgically. Periodic measurements were made of heart rate, systemic and pulmonary arterial pressures, cardiac output, and plasma glucose before and after intravenously-administered glucagon. Values were also calculated for cardia index, total peripheral and pulmonary vascular resistances (TPR and PR), stroke volume (SV), left and right ventricular stroke work (LVSW and RVSW), and left and right ventricular minute work (LVMW and RVMW). Three to five minutes following intravenous doses of 50 μg/kg of glucagon, increases from pre-injection mean values were noted in heart rate (66.9%), cardiac index (33.0%), pulmonary arterial pressure (6.7%), RVMW (36.6%) and LVMW (14.8%). Decreases were observed in systemic pressure (8.4%), TPR (29.3%), PR (16.7%), SV (28.9%), RVSW (30.6%), and LVSW (31.6%). Plasma glucose increased 137.3% over control values thirty minutes after glucagon had been administered. ...