Stimulation of mitochondrial protein synthesis and oxygen consumption by thyroxine in vitro without deiodination to triiodothyronine.

Abstract

Abstract The abilities of triiodothyronine (T 3 ) and thyroxine (T 4 ) to stimulate protein synthesis and oxygen consumption and to alter ADP/O and respiratory control ratios in normal rat liver mitochondria in vitro have been investigated together with determinations of the extent of conversion of T 4 to T 3 . There was no significant differences in the ability of either hormone to stimulate protein synthesis or oxygen consumption. ADP/O and respiratory control ratios were approximately equally depressed by T 4 and T 3 in concentrations (10 and 50 μM) which increased mitochondrial protein synthesis and oxygen consumption. T 4 was not appreciably deiodinated to T 3 , indicating that the hormones are of equal potency in producing these effects in normal mitochondria in vitro .