Does a glucose load inhibit hepatic sugar output? C14 glucose studies in eviscerated dogs

Abstract

A sequence of changes in plasma glucose specific activity is observed in intact dogs when a large amount of C¹² glucose is injected intravenously following the tagging of the circulating glucose by injection of a minute amount of C¹⁴ glucose. Similar changes are observed when the same procedure is applied to eviscerated dogs in which the plasma glucose concentration is being maintained by a continuous infusion of C¹² glucose, this infusion being continued unchanged after the C¹² glucose load is given. These results show that inhibition of hepatic glucose output is not the only or the necessary explanation for the cessation in the exponential fall of plasma glucose specific activity which is seen in the intact dog following an intravenous C¹² glucose load. An alternative explanation of the effect is offered which is based on the slowness of mixing of the injected C¹² glucose load with a part of the body glucose pool.