Conversion of Alanine, Aspartate and Lactate to Glucose and CO2 in Liver from Stress-Susceptible and Stress-Resistant Pigs

Abstract

Rates of conversion of lactate, alanine and aspartate to glucose and oxidation of each to CO2 were determined in incubated liver slices from nine stress-susceptible (SS) and seven stress-resistant (SR) Yorkshire pigs ranging in body weight from 24 to 54 kg. Pigs were screened for stress susceptibility by exposure to halothane at 7 weeks of age. Stress was minimized before slaughter, and liver samples were obtained immediately after death. Rates of lactate and aspartate conversion to glucose were not significantly different between pig types. Mean rates of lactate conversion to glucose in livers of SS and SR pigs were 637 and 413 nmoles/(100 mg X 2 hours), respectively. Mean rates of aspartate conversion to glucose were 441 and 540 nmoles/(100 mg X 2 hours) in SS and SR pigs, respectively. Alanine conversion to glucose in livers of SS pigs was slower than that in SR pigs [527 and 813 nmoles/(100 mg X 2 hours), respectively]. Rates of hepatic gluconeogenesis from lactate probably do not predispose SS pigs to the lactic acidosis observed during the porcine stress syndrome. Rates of lactate, alanine and aspartate oxidation to CO2 in livers of SS pigs were 61, 59 and 76%, respectively, of the rates observed in SR pigs. Decreased rates of substrate oxidation to CO2 may contribute to the development of the syndrome in SS pigs.