1. Thyroid hormones alter Arrhenius kinetics of succinate-2,6-dichloroindophenol reductase, and the lipid composition and membrane fluidity of rat liver mitochondria.
- Author
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Parmar, Dipak V., Khandkar, Milind A., Pereira, Leon, Bangur, Chaitanya S., and Katyare, Surendra S.
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THYROXINE ,THYROID hormones ,ARRHENIUS equation ,FLUIDITY of biological membranes ,MITOCHONDRIA ,PHOSPHOLIPIDS - Abstract
Thyroid-status-dependent changes in lipid/phospholipid profiles in rat liver mitochondria were examined and attempts were made to correlate the observed changes with kinetic parameters of succinate-2,6-dichloroindophenol reductase (SDR) and membrane fluidity. Thyroidectomy caused substantial decrease in the total phospholipid and cholesterol contents; the proportion of all phospholipid components was also decreased significantly (50–100% decrease). The energy of activation, E
1 , for SDR decreased with a concomitant increase in the membrane fluidity. Treatment with physiologic doses or replacement doses of L-thyroxine resulted in partial restoration of lipid/phospholipid components. However, the SDR activity decreased with a simultaneous elevation in the phase-transition temperature and significant decreases in E1 and E2 . Treatment with L-thyroxine restored membrane fluidity to almost euthyroid values. Regression analysis suggested a role for phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine and phosphatidylinositol microdomains in modulating the SDR activity. Membrane fluidity was strongly correlated with total phospholipid, cholesterol, diphosphatidylglycerol and phosphatidyl-inositol, and the ratio of cholesterol/total phospholipid (mol/mol). [ABSTRACT FROM AUTHOR]- Published
- 1995
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