Phosphoenolpyruvate carboxykinase in the small intestine of developing rodents.

Phosphoenolpyruvate carboxykinase activity was found to be high in the mucosa of the small intestine of suckling rats. Activity was higher proximally than distally and decreased to very low values at weaning. After weaning, feeding a high fat diet or starvation did not result in elevation of the low intestinal activity in rats. However, in mice, who also showed high activity in the suckling period, starvation, but not diet, did cause a rise. Since fructose-diphosphatase was also found in the intestinal mucosa of suckling rats, it is suggested that gluconeogenesis may occur in this tissue in the neonatal period.