Effect of Dietary Lipids on Myocardial Norepinephrine Content and Field Stimulation-Mediated Release of Norepinephrine from Perfused Neonatal and Adult Rat Hearts

The effects of dietary lipids on the content and release of norepinephrine and on the overflow of norepinephrine after α-adrenoeeptor blockade with phentolamine were investigated in isolated perfused rat hearts. Pregnant rats were fed Purina Rodent Chow (reference diet) or a semisynthetie diet containing 16% (wt/wt) of either coconut oil (saturated fatty acids) or sunflower oil (unsaturated fatty acids). Neonatal pups were exposed to the diet via maternal milk and weaned rats were maintained on the same dietary lipid supplementation. Coconut oil caused a significant decrease in cardiac norepinephrine in all age groups when compared with the reference diet (p < 0.01). Sunflower oil caused a significant increase in cardiac norepinephrine at 14 and 21 days of age when compared with coconut oil (p < 0.05). Hearts prelaheled with [‘H]norepinephrine were stimulated with supramaximal voltage (5 Hz, 2 ms duration. 300 pulses). At 14 and 21 days, coconut oil caused a significant decrease in norepinephrine release when compared with sunflower oil (p < 0.05). The releases of norepinephrine from hearts exposed to sunflower oil diet and the reference diet were comparable. These alterations in neuronal storage and exocytotic release of norepinephrine may he due to dietary-induced membrane perturbations. Phentolamie (10–10–M) caused a dose-related increase in norepinephrine release following stimulation (supramaximal voltage 2.5 Hz. 150 pulses) of adult rat hearts from all dietary groups. However, the increase above control values was highest for coconut oil and lowest for sunflower oil (p < 0.01). suggesting changes in receptor sensitivity. It appears that dietary lipid supplementation in the developing and adult rat could affect the myocardial α-adrenoeeptor microenvironment which could cause changes in the prejunctional α-adrenoceptor neuronal function.