The influence of different dietary fat sources on tissue corticosterone concentration in rats

Forty-one rats were divided into six groups assigned to one of six diets co ntaining three different fat types (sunflower oil, lard or 50:50 (wiw) blen d of sunflower and lard) at one of two levels (5 or 30%) to determine the e ffect on the corticosterone (Cs) level in the cytosol fraction of the adren al glands, heart muscle and aorta in rats. Plasma cholesterol concentration s and body composition were also measured. The diet with 5% lard significantly increased adrenal Cs compared with diet s with 5% sunflower oil or 5% blend. Marked elevations in Cs level in the a orta were evident in rats fed diets with 5 and 30% sunflower oil in compari son with rats fed the 5 and 30% blend of lard and sunflower oil. In additio n, the Cs level in the aorta in rats fed the diet with 30% sunflower oil wa s significantly higher than in rats fed the diet with 30% lard. The diet co ntaining 5% sunflower oil markedly elevated the Cs level in rat heart muscl e compared with the diet containing a 5% blend of the two fats. Unexpectedl y, there were no significant effects of the experimental diets on plasma ch olesterol concentrations. Moreover, rats fed diets containing 30% fat had h igher body dry matter and fat percentages, but lower protein and ash percen tages compared with the rats fed diets containing 5% fat. The percentages o f fat, protein and ash in the body were not affected by the type of dietary fat, but rats offered lard diets had a higher percentage of dry matter and fat than rats fed mixed fat diets.