Thyroid hormone treatments differentially affect the temperature kinetics properties of FoF1 ATPase and succinate oxidase as well as the Lipid/Phospholipid profiles of rat kidney mitochondria:: A correlative study

Effect of thyroidectomy ( Tx) and subsequent treatment with 3,5,3'-triiodo- L- thyronine ( T-3) or replacement therapy ( TR) with T-3 + L- thyroxine ( T-4) on the temperature kinetics properties of FoF(1) adenosine triphosphatase ( ATPase, ATP synthase, H+- translocating ATP synthase EC 3.6.3.14) and succinate oxidase ( SO) and on the lipid/ phospholipid makeup of rat kidney mitochondria were examined. Tx lowered ATPase activity, which T-3 treatment restored. SO activity was unchanged in Tx but decreased further by T-3 treatment. TR restored both activities. The energies of ATPase activation in the high and low temperature ranges ( EH and EL) increased in the Tx and T-3 animals with decrease in phase transition temperature ( Tt). TR restored EH and EL but not Tt to euthyroid levels. EH and EL of SO decreased in Tx animals. T-3 and TR restored EH whereas EL was restored only in the TR group; Tt increased in both groups. Total phospholipid and cholesterol contents decreased significantly in Tx and T-3-treated animals. In Tx animals, sphingomyelin ( SPM) and phosphatidylcholine ( PC) components decreased, while phosphatidylserine ( PS) and diphosphatidylglycerol components increased. T-3 and TR treatments caused decreases in SPM, phosphatidylinositol and PS. PC and phosphatidylethanolamine ( PE) increased in the T-3 group. TR resulted in increased lysophospolipids and PE. Changes in kinetic parameters of the two enzymes were differently correlated with specific phospholipid components. Both T-3 and T-R regimens were unable to restore normal membrane structure- function relationships.