Effects of a Fat-Free Diet on Growing Male Rats with Special Reference to the Endocrine System

Abstract

Thirty male Holtzman rats were fed, from the time of weaning and for a period of 20 weeks, a synthetic diet completely devoid of fat. Eighteen animals maintained under identical conditions were fed Purina Laboratory chow to serve as controls. Constant findings in the rats fed fat-free diets were impaired growth, the body weight attained being 66% that of controls; typical skin lesions on tail, feet and back, beginning after 9 weeks on the deficient diet; and increased oxygen consumption demonstrable as early as two weeks. Autopsy after 20 weeks on the deficient diet revealed the brain, adrenals, liver, heart and kidneys to be significantly heavier than in controls on a relative body weight basis, but the thyroid smaller. Microscopic study showed inter-tubular accumulations of blood in the kidneys, the characteristic thickening of the epidermis, as we have previously described in the female rat, and accumulation of fatty droplets around hepatic veins. There was increased capillary vascularity of the myocardium. In spite of insignificant relative weight changes in the testes, prostate or seminal vesicles, the seminiferous tubules of all deficient rats showed signs of degeneration consisting of varying degrees of inter-cellular and intra-cellular vacuolations and reduction in spermatids and mature spermatozoa. Other groups of male rats maintained on the fat-free diet for periods of only two and 5 weeks showed similar differences from controls in body weight and weight of brain, liver, heart, kidney and thyroid, indicating that defimite effects of fat deficiency are present long before the appearance of skin lesions.