A study of the kinetic behaviour of glucose based on simultaneous estimates of influx and phosphorylation in brain regions of rats in different physiological states

Abstract

Results from the application of a procedure that allows simultaneous estimation of the rates of glucose transport from blood and of glucose phosphorylation in discrete regions of the brain are given for groups of rats displaying chemically induced motor disturbances. The procedure is based on sequential injections of [ 14C]- and [ 3H]-2-deoxyglucose followed a few minutes later by focused microwave irradiation to the head. Control conscious rats were used and rats displaying either whole body tremors, hind-limb rigidity or choreoathetotic movements induced by synthetic pyrethroid compounds. For individual rats estimates of 5 parameters were obtained in up to 16 brain regions. In addition brain tissue and plasma glucose concentrations were determined. The 5 parameters were: (1) rate of total glucose influx from plasma; (2) rate of glucose phosphorylation (equivalent to net influx); (3) rate of glucose efflux; (4) half-life of free glucose in brain; and (5) PS-product expressed as the ratio of the rate of glucose influx to plasma glucose concentration. For each parameter significant differences between regions were found in all groups of animals including conscious controls. The mean values for the somatosensory cortex of control rats were parameter: (1) 2.02 μmol/g/min; (2)1.11 μmol/g/min; (3) 0.91 μmol/g/min; (4) 0.94 min; and (5) 0.196 ml/g/min. A high correlation was observed between the rate of total glucose influx and the rate of glucose phosphorylation for all brain regions in all groups of rats. This finding is discussed in terms of a synchronized regulatory mechanism on the glucose transport carrier of capillary endothelial cells and on the functional hexokinase V max activity within brain cells.