Influences of dietary fats on the coronary flow and oxygen consumption of the isolated rat heart.

The influence of various diets on the coronary flow (Qcor) and oxygen consumption (VO2m) of Langendorff-perfused rat hearts was studied. The diets contained 23 percent of the total amount of calories as proteins and sufficient amounts of minerals and vitamins, while the amounts of starch and type of fat were varied. In the Langendorff set-up, the perfusion pressure (Pp), and/or the developed left ventricular pressure (PD) were varied to change Qcor and VO2m. At Pp = 50 and 90 mm Hg, Qcor and VO2m of the isolated hearts of rats fed 50 percent of the total number of calories (cal%) as sunflower seed oil (50 SSO) or 50 cal% palm oil (50 PO) for 3 days were 10--20 percent higher than those of the hearts of rats fed pellets (11 cal% fat). At Pp = 80 mm Hg and at various levels of PD, Qcor of the isolated hearts of rats fed 50 SSO or 45 PO + 5 SSO for 3 months was about 20 percent higher than that of the isolated hearts of rats fed a high carbohydrate diet. No differences were found in VO2m or in the maximum obtainable value of PD. When rats were fed mixtures (total amount of fat 50 cal%) of SSO and hardened coconut oil (CO) for 3 days, Qcor increased with increasing dietary SSO. The value of Qcor of the isolated hearts of rats fed a high carbohydrate diet containing 5 cal% SSO was in between the values of the groups fed 50 SSO and 45 CO + 5 SSO. Perfusion of the latter two groups of hearts with substrate-free medium increased Qcor by about 35 percent. The total hypoxanthine + inosine output in these two groups of hearts was about 4.0 nmoles-min-1, and remained contstant during perfusion with substrate-free medium. We conclude that the composition of the diet influences the coronary flow of isolated perfused rat hearts. The amount and the type of dietary fat influence both the magnitude and the direction of the effects. The relationship between the type of dietary fat and its effects on coronary flow is complex.