The effect of the administration of insulin to the hypophysectomized rat on the incorporation of amino acids into liver proteins in vivo and in a cell-free system

Abstract

Hypophysectomized rats treated with insulin incorporated more of an intravenously administered dose of radioactive amino acids into the proteins of liver mitochondria, microsomes and soluble fraction than did untreated hypophysectomized rats. The distribution of radioactivity in the microsomal particles, and in the portion of the microsomes soluble in deoxycholate, indicates that treatment with insulin tends to restore the diminished ability of the microsomal particles of the liver of hypophysectomized rats to take up amino acids and assemble them into polypeptide chains. Insulin treatment of hypophysectomized rats diminished the time elapsing before the maximum specific activity of the protein of the ribonucleoprotein microsomal particles was reached. Experiments with a cell-free system in vitro showed that insulin treatment of hypophysectomized rats enhanced the diminished ability of the liver microsomes to incorporate amino acids into protein. The results also suggest a small rise in the ability of the soluble fraction of liver from hypophysectomized rats to produce amino acids for incorporation into proteins. Cell-free preparations from the livers of male and female hypophysectomized rats showed that the female hypophysectomized rats responded more quickly and completely to the stimulating effects of insulin treatment than male hypophysectomized rats.