Stimulation by Thyroxine of Amino Acid Incorporation Into Mitochondria

Abstract

Rat liver mitochondria, prepared by a procedure designed to rid them of soluble RNA and ribo-somes, incorporate amino acids into acid-precipitable material when incubated with potassium, magnesium, inorganic phosphate and an oxidizable substrate. L-Thyroxine (T4) and a number of its analogues, added in vitro, markedly stimulate this incorporation. Their effect is dependent on the presence of these same cofactors. Both control and T4-stimulated incorporation are sensitive to low concentrations of chloramphenicol, puromycin and tetracycline. High concentrations of ribonuclease and deoxyribonuclease do not inhibit either control or T4-stimulated incorporation.