[Thyroid hormones and the electrical stability of rat liver mitochondrial membranes].

The electrical stability of mitochondrial membranes isolated from the liver of normal, hypothyroid, hyperthyroid (0.1 mg L-thyroxine per 100 g bw for 9 days) and thyrotoxic (4 mg L-thyroxine per 100 g bw for 6 days) rats was investigated. The electrical stability of mitochondrial membranes was estimated by the amount of potassium acetate required for electrical breakdown of the mitochondria. Of the four mitochondrial populations, the organelles of hyperthyroid and thyrotoxic animals had the most stable membranes, whereas the electrical stability of the mitochondria of normal and hypothyroid rats was approximately the same. It is assumed that the increased electrical stability of the mitochondria seen in hyperthyroid conditions is linked with the hormone-induced modifications in the composition of membrane phospholipids rather than with a direct action of excess thyroxine on the organelles.