Stimulation of Glucagon Secretion by Scorpion Toxin in the Perfused Rat Pancreas

Toxin from the scorpion Leiurus quinquestriatus was used to release norepinephrine from sympathetic nerve endings in the perfused rat pancreas. Addition of toxin, 10μg./ml., to perfusate containing 0.3 mg./ml. glucose caused a large increase in release of norepinephrine and glucagon. Glucagon secretion was suppressed by perfusate containing 3.0 mg./ml. glucose but still responded to stimulation with scorpion toxin. Atropine, 10 μM, had no effect on either norepinephrine or glucagon release in response to scorpion toxin. The release of glucagon was blocked by 100 μM propranolol, 10 μM phentolamine, or 30 μM phenoxybenzamine. Somatostatin, 55 nM, did not affect the release of norepinephrine by scorpion toxin but totally inhibited the glucagon response. These results suggest that pharmacologic stimulation of the adrenergic nerve endings in the rat pancreas can elicit a rapid release of glucagon. This response can be prevented by appropriate concentrations of either alpha or beta adrenergic blocking agents or somatostatin.