Urea and ammonia in urine and plasma of fed-mid-pregnant rats.

In the rat, mid-pregnancy seems to be related to an active nitrogen metabolism. In the present work we studied how the plasma homeostasis and the urinary nitrogen excretion of urea and ammonia could be altered during this period. Urea and ammonia plasma levels do not show significant changes, whereas, their urinary excretion is increased at mid-pregnancy. When urea levels in urine are corrected by the urinary creatinine content and the food intake, we found lower values in pregnant than in virgin rats. Thus, the organic nitrogen is more spared during pregnancy than before impregnation without any significant changes in the urea and ammonia plasma concentrations.