Deficient synthesis of factor VII by liver tissue of fetal and newborn rats

Abstract

The deficiency of circulating factor VII in the newborn human being was confirmed for the newborn rat and its etiology studied. The ability of liver slices from fetal, newborn and adult rats to synthesize factor VII in vitro was compared under standard conditions. Fetal tissue had about 1/20 and newborn tissue about 1/3 the capacity of adult tissue to form this factor. Although a deficiency of vitamin K has been considered the cause of the clotting factor deficiencies at birth, supplementation of the rat tissue, either with vitamin K added to the liver slices in vitro or vitamin K given to prepartum mother rats in vivo, resulted in only minor improvement of the synthetic rate. Extracts of fetal liver were studied for the presence of an inhibitor of factor VII synthesis and extracts of adult tissue for the presence of a stimulator, but neither could be detected. It was concluded that a functional immaturity of liver enzyme systems involved in synthesis of factor VII exists at birth.