[Postnatal development of gluconeogenic key enzymes, phosphoenolpyruvate carboxykinase and pyruvate carboxylase, in pig liver].

Abstract

Using a radiochemical method the activity of the gluconeogenic key enzymes phosphoenolpyruvate carboxykinase (PEPCK) and pyruvate carboxylase (PC) was determined in liver homogenates of 58 piglets (from birth to 10 days of life), 4 weaners and 18 fattening pigs. Simultaneously, the cytosolic PEPCK activity was estimated. In liver of newborn piglets (immediately after birth without suckling) total PEPCK activity is one half, cytosolic PEPCK activity one sixth and PC activity one half of that occurring in adult pig's liver. During regular suckling within the first 12 h of life, the total PEPCK activity of piglet liver rises slowly, however, cytosolic PEPCK activity increases 3 to 4 times and PC activity in the mitochondria twice. After the 2nd day of life the activity of both enzymes reaches a level which is kept during the whole suckling period: total PEPCK activity is 1.5 to 2-fold, cytosolic PEPCK activity is 2 to 3-fold higher, and PC activity is at the level existing at birth. In weaners cytosolic PEPCK activity further rises to the level existing in the liver of adult pigs. The PEPCK and PC activities in the liver at birth enables the piglet for gluconeogenesis, but due to the postnatal increase of enzyme activities, the prerequisites for an intensive synthesis of glucose are given only after the 2nd day of life.