Effects of thyroid hormones on the bypasses of the antimycin A block in the bc1 complex of rat liver mitochondria.

Abstract The effect of thyroid hormones on the electron flow through the bc 1 complex of rat liver mitochondria was studied using two dye bypasses of the Antimycin A block of the bc 1 complex by the method of Alexandre and Lehninger (Biochim. Biophys. Acta 767:120; 1984). Bypass respiration rates with both DCIP (2,6-dichlorophenolindophenol) and TMPD (N,N,N′,N′-tetramethyl- p -phenylenediamine dihydrochloride) were elevated in the hyperthyroid rats and depressed in the hypothyroid groups compared to the euthyroid controls. T 3 treatment of hypothyroid rats returned the bypass rates to control levels in 24 hours with the TMPD dye but not for the DCIP. This further demonstrates that different portions of the bc 1 complex respond individually to the thyroid state.