Effects of Giving a Fat-free Diet for up to 10 Weeks on the Male Weanling Rat.

When weanling rats are reared on a fat-free diet for about 10 weeks they develop, as originally shown by Burr & Burr (1929), certain signs of a nutritional deficiency. The signs can be cured or prevented by the inclusion of essential fatty acids (EFA), as linoleic acid, in the diet and the condition is therefore termed EFA deficiency. The weanling male rat has been used extensively in studies concerning EFA deficiency. In this animal the deficiency is characterized by a number of clinical signs such as lower weight gain, scaly skin, partial necrosis of the tail, increased water consumption. B.esides this, the fatty acid pattern in the tissues is different from that in the normal rat. Generally, the concentrations of di-, tetra-, pentaand hexaenoic acids are lower, whereas the concentrations of trienoic and monoenoic acids with 16-18 carbon atoms are higher in deficient than in normal animals (Caster & Holman, 1961 ; Mohrhauer & Holman, 1963). The early changes in the polyenoic fatty acid pattern in the weanling rat fed on an EFA-free diet have not been studied previously. Aaes-Jorgensen & Holman (1958) have demonstrated that the changes in testes polyenes are confined to the first 6 weeks of feeding after which the concentrations remain approximately constant. Brenner, Mercuri & De Tomis (1962) found, in accordance with this, that the polyenoic acid concentration of heart tissue was the same after 13 weeks as after 8 weeks of feeding, and that the concentration of dienoic acid in liver after 8 weeks was very nearly nil. In experiments with day-old chicks, Machlin (1961) observed that EFA deficiency is reflected in the fatty acid pattern of heart and liver after 1-2 weeks, and Holman (1956) has published a depletion curve for mice showing a rapid fall in linoleic acid content during the 1st week on the deficient diet. The change in linoleic acid content (percentage of total fatty acids (TFA)) in depot fat of weanling mice fed on a fat-free diet has been studied by Tove & Smith (1959) for 25 days. It appeared that the linoleic acid concentration in relation to time followed the equation of a first-order reaction. A quantitative description of the changes in polyenoic acid concentrations in plasma, heart and liver during the first 10 weeks of EFA deficiency of rats given deficient diets from weaning is given in the present paper. Further, the weight of body, heart and liver, as well as the dermal signs, are reported.