Transport of plasma FFA in cats; effect of hypothalamic stimulation

Two tracer methods, repetitive single injection of [3-H]palmitate and continuous infusion of [1 minus 14-C]palmitate, were applied simultaneously to study tracer kinetics of the free fatty acid (FFA) miscible pool in anesthetized cats before, during, and after electrical stimulation of the hypothalamus. The results indicated that the FFA pool of the cat behaved as though it consisted of two compartments which exchange FFA with each other. The data were analyzed according to a two-compartmental mammillary system model. The space of the central compartment which represents the plasma was found to be 74 ml/kg body wt. No anatomical significance could be unequivocally ascribed to the peripheral compartment. The variables of the model system were determined for each cat, and a highly significant positive linear relationship between the net FFA transport (mumol/min) and the total quantity of FFA (mumol) in both compartments was established by a regression analysis of the control data. No significant changes were observed in this relationship during or following hypothalamic stimulation which had a significant effect on the plasma FFA level. This result suggests that hypothalamic stimulation affects FFA mobilization by modifying the rate of FFA inflow into the circulation, while the mechanisms for clearing FFA from the plasma are not altered.