Solubilization of brain mitochondrial hexokinase by thiopental

The control of hexokinase activity probably is accomplished by regulating the partitioning of the enzyme between soluble and particulate forms, the latter being more active. In the present investigation we have examined the thiopental effect on the cerebral hexokinase distribution. In anesthesia, after administration of thiopental to male Sprague Dawley rats, the increase of the soluble fraction of hexokinase was dose dependent. The change in the intracellular hexokinase distribution was reversible and lasted as long as general anesthesia existed. Also in experiments in vitro a solubilization of the mitochondrial hexokinase by thiopental (0.1--1 mM) occurred; it was depending on drug concentration. An inhibition of hexokinase was found neither in the total brain extract, nor in the soluble or the particulate fraction. The results suggest that phosphorylation of glucose in brain may be suppressed in anesthesia by shifting hexokinase activity from a more active mitochondrial form to its less active soluble form. This effect seems to be caused by a direct action of thiopental and is obviously correlated with anesthesia.