Effect of Hypophysectomy on Lipid Composition in the Immature Rat

Abstract

Studies of the effect of hypophysectomy on the composition of the lipids of hearts, kidneys, livers, epididymal fat pad and testes of immature rats of the Sprague-Dawley strain are reported. Hypophysectomized weanling rats (3 weeks of age) were killed in groups of six at selected intervals over a 44-week period and compared to normal animals of the same age fed the same diet. Feed consumption, growth and weights of organs of both hypophysectomized and normal animals were measured. The hypophysectomized animals grew to only about one-third the size of normal animals. The hearts, livers, kidneys and epididymal fat pads of the hypophysectomized animals consisted of approximately the same percentage of the body weight as those of the normal animals. In contrast, the testes of the hypophysectomized animals were only about one-tenth the weight of those of the normal animals. After 18 weeks, most of the hypophysectomized animals exhibited shaggy coats, scaly tails and feet, characteristic of the dermal symptoms of an essential fatty acid (EFA) deficiency. The effect of hypophysectomy, 3 weeks after the operation (6-week-old animals), was reduction in the total amount of testicular lipid with a pronounced change in its composition, namely, an increase in the percentage of neutral lipids and a corresponding decrease in the percentage of phospholipids. As the animals became older, this trend was reversed. There was a decrease in the percentage of neutral lipid and a relative increase in the percentage of phospholipids. Changes also occurred in fatty acid composition of the organs of the hypophysectomized animals. In general, these changes consisted of an increase in the percentage of linoleic acid and corresponding lower percentages of arachidonic (C20:4) and docosapentaenoic acids (C22:5), indicating impairment in the interconversion of unsaturated fatty acids.