CARDIAC-PERFORMANCE IN RELATION TO OXYGEN-SUPPLY VARIES WITH DIETARY-LIPID COMPOSITION IN STURGEON

Dietary polyunsaturated fatty acids (PUFA) of the n-3 series that have beneficial effects on mammalian heart function are typically found at high levels in fish tissues. The effects of dietary fatty acid compos ition on cardiac function were investigated in the sturgeon. When comp ared with sturgeon maintained for 1 yr on a diet enriched with saturat ed fatty acids (SFA) (the coconut oil-supplemented diet, GOD), sturgeo n maintained on a diet enriched with n-3 PUFA (the fish oil-supplement ed diet, FOD) had higher myocardial 20:5(n-3) and lower 20:4(n-6) cont ent with a consequent decrease in the n-6-to-n-3 ratio (from 0.86 to 0 .25) and a,lower intrinsic in vitro heart rate (22.0 +/- 1.5 vs. 29.9 +/- 1.0 beats/min) and cardiac power output (PO) (0.33 +/- 0.08 vs. 0. 48 +/- 0.03 mW/g), but had a greater in vitro scope for cardiac work ( almost twice the maximal-to-basal PO ratio). Reducing the oxygen suppl y to the hearts significantly decreased, by similar to 40%, the maxima l in vitro PO in the COD group of animals but had no effect in the FOD group. These differences in performance were not reflected in heart r ate or blood pressure in vivo, either in normoxia or hypoxia. Addition of vitamin E as an antioxidant to the diets reduced intrinsic heart r ate by similar to 25% but did not influence the effects of dietary fat ty acid composition on in vitro cardiac performance. The results indic ate that dietary n-3 PUFA can have beneficial effects on the resistanc e of the fish heart to environmental stressors such as hypoxia.