Comparison of rat brain and heart mitochondrial hexokinase solubilized by methohexital

The purpose of the present investigation was to compare the solubilizing effect of methohexital on the mitochondrially bound hexokinase activity in brain and heart tissue of the rat. Experiments were performed using intact rats, the isolated perfused rat brain and heart as well as mitochondrial fractions from rat brain and heart tissue. It was shown that bound hexokinase activity was significantly solubilized by methohexital in brain tissue in vivo and in the isolated perfused rat brain but no effect was demonstrable in heart tissue. When mitochondrial fractions were incubated with methohexital in vitro, hexokinase activity was significantly solubilized from brain mitochondria but only slightly from heart mitochondria although glucose-6-phosphate was able to displace hexokinase also from heart mitochondria. The results suggest that mitochondrially bound hexokinase activity in brain tissue is particularly sensitive against the solubilizing effect of anesthetics. This effect could contribute to the sensitivity of brain function and metabolism against anesthetic drugs.