Replacement rate of free fatty acids in fasted rats adapted to a high-protein diet
Foss, M.C.; Kettelhut, I.C.; Migliorini, R.H.
Brazilian Journal of Medical and Biological Research 22(12): 1519-1525
1989
ISSN/ISBN: 0100-879X PMID: 2641359 Document Number: 335117
Free fatty acid (FFA) mobilization was studied during 72 h of fasting in 10 adult male cats fed on a meat diet (63% protein, 18% fat, 6% carbohydrate, w/w) or a carbohydrate-rich diet (15% protein, 10% fat, 70% carbohydrate), and in 10 male Wistar rats adapted to a high-protein, carbohydrate-free synthetic diet (70% casein, 8% fat) or a balanced synthetic diet (66% carbohydrate, 17% casein, 8% fat). FFA concentration in plasma was determined by the method of Dole and Meinertz. Results showed that fasted cats and rats on the high-protein diet had reduced rates of plasma FFA increase. Their blood glucose was unchanged but higher than that of controls fed on carbohydrate-rich diet after fasting for 24 (rats) or 48 h (cats). The steady-state rate of plasma FFA replacement was estimated with a continuous infusion of 1-[14C]-palmitate (5 micro litre/min for 1 h) in anaesthetized fed and fasted rats with plasma FFA levels ranging from 0.30 to 1.45 micro mol/ml, adapted to the high-protein or to the balanced diet. Under these dietary conditions, FFA replacement rates were linearly related to concentration of plasma FFA. However, the slope of the regression line was steeper for rats on the high-protein diet. It is concluded that, for the same concentration of plasma FFA, replacement rates for rats adapted to the high-protein diet were higher than for controls. The higher rates of FFA replacement required in situations demanding an increased supply of FFA for animals on high-protein regimens are attained with smaller increases in plasma FFA concentration.