Ammonia Production by the Pregnant Uterus 1

Abstract

Summary

The arterial-venous differences of ammonia and oxygen were measured across the uterine and umbilical circulations in nonanesthetized, chronic sheep preparations from 47 to 155 days of gestation. In all cases, ammonia was excreted from the uteroplacental unit into both the uterine and umbilical circulations. In early gestation (70 days), the gravid uterus excretes into the maternal blood ~55 μol of ammonia/mmole of oxygen consumed and it can be estimated that the ratio of nitrogen excreted by the uterus as ammonia to the combined total nitrogen requirements for both growth and ammonia excretion is ~44%. Late in gestation, the gravid uterus excretes ~16 μmol of ammonia/mmole of oxygen consumed. This represents ~12% of fetal nitrogen requirements.