Metabolism of 1-14C Palmitic Acid in Goats in Various Metabolic States

1-14C Palmitate albumin complex was constantly infused intravenously through jugular catheter for four hours in goats in three metabolic states. I, 72-hr fasted, phlorizinized, and nonlactating; II, normally fed and lactating; III, 72-hr fasted, phlorizinized, and lactating. The 14C activity was measured in ketone bodies and various lipid fractions of plasma at various time intervals, and quantitation of these fractions was carried out. The estimated percentage of C atoms of plasma ketone bodies derived from plasma free fatty acids were 89, 41, and 303 in the respective three trials. The ratio between fl-hydroxybutyrate and acetone + acetoacetate changed from 4:1 in Trial II to 1.4:1 in Trial III; at the same time the concentration of total ketone bodies was three times higher in Trial III. The turnover rates of free fatty acids were 4.2, 4.3, and 7.9 mg/kg/min for Trials I, II, and III, respectively. The corresponding turnover times were 4.6, 1.8, and 3.1 rain. Production of ketone bodies from free fatty acids and free fatty acid turnover rate were directly related to the stress conditions imposed on the animals. In all metabolic states the major ~4C activity of plasma was recovered in the free fatty acid fraction, whereas in liver most of the activity was in glycerides. Adipose tissue samples in all the trials contained only a small amount of a4C activity.