Infusion of growth-hormone release inhibiting hormone (G.H.-R.I.H.) in four fasting subjects reduced plasma glucagon and insulin concentrations to undetectable levels and this was associated with a highly significant decline in plasma-glucose (28±S.E.M. 3 mg. per 100 ml. in 1 hour, p< 001). When plasma-glucagon was maintained by an exogenous infusion, at a level which did not itself significantly alter glucose or insulin concentrations, G.H.-R.I.H. administration resulted in a rise in the mean plasma-glucose (20±10 mg. per 100 ml.). It is concluded that, in man, glucagon plays an important part in the maintenance of fasting plasma-glucose.
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