[Effect of insulin on brain pyruvate dehydrogenase in the rat. (Preliminary note)]

The activity of both active and total pyruvate dehydrogenase (E.C.1.2.4.1) is substantially reduced in the rat brain 24h after alloxan administration. Effects are partially removed by insulin administration. Ca++ and Mg++ produce: a) a considerable conversion of the inactive form of pyruvate dehydrogenase into its active form in a preparation from the brain of normal rats and of rats treated with insulin; b) no conversion in a preparation from the brain of rats treated with alloxan; c) some conversion in a preparation from the brain of rats treated with both alloxan and insulin. Active and total pyruvate dehydrogenase from the brain of rats treated with alloxan are activated by a preparation obtained from a mixture of entire plasma membranes-mitochondria from normal and from alloxan-treated rats, or from insulin-treated and alloxan treated rats. The oxygen uptake, the respiratory control index and the ADP/O ratio in mitochondrial preparations obtained from the brain of rats treated with alloxan show no modification at all.