Pyruvate Carboxylase and Phosphoenolpyruvate Carboxykinase Activity in Developing Rats: Effect of Manganese Deficiency

The activities of two liver gluconeogenic enzymes, pyruvate carboxylase (PC) and phosphoenolpyruvate carboxykinase (PEPCK) as well as plasma glucose were measured in manganese-sufficient and manganese-deficient rats from birth to 30 d of age. Initial (d 0) PC activity was similar in the two groups. PC activity increased 1.5-fold in control pups and 2.4-fold in manganese-deficient pups from d 0 to 3 postnatally. PEPCK activity increased 1.5-fold in control pups and 2.2-fold in manganese-deficient pups from d 0 to 3. By d 8, the activity of PEPCK in manganese-deficient pups was 60% of control levels. Compared to control pups, plasma glucose concentration was lower in manganese-deficient pups on d 1 and 2, coinciding with a period of high neonatal mortality. These findings suggest that glucose homeostasis in the newborn may be compromised by manganese deficiency and may support the concept that changes in cellular manganese concentration may be important in the regulation of carbohydrate metabolism.