Changes in evolution of free epinephrine, norepinephrine, and vanillylmandelic acid in the urine of rabbits during late pregnancy and parturition.

The present study describes evolutionary changes in urinary excretion of epinephrine, norepinephrine, and vanillylmandelic acid during pregnancy and parturition. Both the catecholamines and their metabolite were determined in 24 hour urine samples of rabbits from day 13 of pregnancy. During 13 and 28 days of gestation, urinary excretion of epinephrine was at its lowest value. As compared to normal rabbits, an increase of 135 per cent in epinephrine excretion during day 30 of pregnancy was observed. Norepinephrine excretion reached its maximum level during day 13 but constant declines occurred afterward. Contrary to epinephine, urinary excretion of norepinephrine was at the highest value days 23 and 30 of pregnancy. After day 19 vanillylmandelic acid declined continuously up to day 30. During parturition vanillymandelic acid and norepinephrine excretion returned to the control values but epinephrine remained slightly higher. These alterations in catecholamine urinary excretion have been suggested as a consequence of modified endocrine and sympathetic activity.