2-Deoxyglucose stimulates the release of insulin and somatostatin from the perfused catfish pancreas

Glucokinase was proposed to function as a glucose sensor in pancreatic B-cells, acting possibly as a pacemaker of the rate of glycolysis. Glucose, mannose, and 2-deoxyglucose are good substrates of glucokinase which are easily taken up into B-cells. Glucose and mannose are well-known stimuli of insulin release in mammals and fish. I report here that 2-deoxyglucose is also a strong stimulus of insulin and somatostatin release from the in vitro perfused pancreas (i.e., splenic Brockmann body) of channel catfish (Ictalurus punctatus). This is surprising because the product of the glucokinase-catalyzed phosphorylation of 2-deoxyglucose. 2-deoxyglucose-6-phosphate, cannot be metabolized further at an appreciable rate. 3-O-Methylglucose, which does not bind appreciably to mammalian glucokinase, stimulated neither insulin nor somatostatin release. Glucosamine, which binds tightly to glucokinase but is phosphorylated only at a very low rate, did not stimulate insulin release either, but did cause a small amount of somatostatin to be released. The results suggest that glucose-activated glucokinase itself may serve as a signal molecule in glucose recognition by B- and D-cells.