Effect of beef tallow diet on alpha 2-adrenergic receptor binding in rat brain regions

We examined the effects of dietary fats consisting of different fatty acids on alpha 2-adrenergic receptor binding in the hypothalamus and cerebral cortex. Sprague-Dawley male rats were meal-fed isoenergetic diets based on safflower oil or beef tallow for 8 weeks. alpha 2-Adrenergic receptor bindings were determined with [3H]para-aminoclonidine. Binding affinities of alpha 2-adrenergic receptor in the hypothalamus and cortex were significantly higher in the beef tallow diet group. The values of the polyunsaturated/saturated fatty acid ratio and the fluidity of the plasma membrane in the hypothalamus and cortex were lower in the beef tallow diet group than in the safflower oil diet group. These results suggest that the beef tallow diet decreases membrane fluidity by altering the fatty acid composition in rat brain regions. Consequently, alpha 2-adrenergic receptor binding affinities in the brain regions are higher in rats fed the beef tallow diet than in rats fed the safflower oil diet.