The relationship of mitochondrial swelling to thyroxine-stimulated mitochondrial protein synthesis.

Abstract

The effects of thyroid hormones and other swelling agents upon mitochondrial volume and upon uptake and incorporation of leucine by normal rat liver mitochondria have been studied in vitro in the medium usually employed for protein synthesis. The lowest concentration of T4 (10 μM) which consistently caused swelling also stimulated amino acid incorporation; both increased as the concentration of T4 was increased to 50 μM. High levels of T4 (ξ100 μM) caused further swelling but inhibited incorporation.The ability of analogues of T4 to stimulate incorporation paralleled their ability toproduce swelling. Inhibition of protein synthesis by chloramphenicol did not alter T4-induced swelling. Of other agents tested, Pi and Fe+ caused swelling without affecting incorporation. Other cations (Ca+, Zn+, Cu+, Ag+ and Hg+) and steroid hormones (progesterone and deoxycorticosterone acetate) markedly inhibited incorporation while causing variable degrees of swelling. The fatty acids (myristic and palmitic acid) also inhi...