Effects of dietary fat supplementation on inositol phosphate release and metabolism in rat left atria.

Eight weeks dietary supplementation with oils enriched in saturated fats, n-6 polyunsaturated fats and n-3 polyunsaturated fats resulted in a reduced inositol phosphate response in isolated rat left atria. Reductions in both basal activity and norepinephrine-stimulated activity were observed. Diets supplemented with n-3 polyunsaturated fats produced a greater decrease in the norepinephrine-stimulated release than the other dietary groups. In addition, supplementation with n-6 polyunsaturated fats resulted in higher levels of the Ca(2+)-releasing compound inositol(1,4,5)trisphosphate while addition of n-3 fats eliminated accumulation of inositol(1, 4)bisphosphate in response to norepinephrine. The reduction in inositol phosphate accumulation observed in all fat-supplemented groups demonstrates the need for caution in choosing relevant control groups in such dietary studies. The specific effects of n-6 and n-3 polyunsaturated fats on individual inositol phosphate isomers demonstrates subtle effects on inositol phosphate metabolism, the significance of which requires further investigation.