Impairment of citrulline synthesis during late pregnancy and lactation in rats.

Synthesis of citrulline by rat liver mitochondria was investigated during late pregnancy and early lactation. It was strongly decreased over all the period studied except during delivery, where a sudden rise was observed. The mitochondrial enzymes carbamoylphosphate synthetase I (ammonia) (EC 6.3.4.16) and ornithine carbamoyltransferase (EC 2.1.3.3) did not fall significantly during this period, although carbamoylphosphate synthetase I (ammonia) was slightly decreased antepartum. Citrulline synthesis was found significantly correlated to N-acetylglutamate concentration in mitochondria throughout the period considered. On the other hand, low levels of N-acetylglutamate could be explained by low activity of N-acetylglutamate synthase (EC 2.3.1.1).