Change in pharmacokinetic character of a p-phenyl benzoic acid in developing fetus of rat.

The change in the pharmacokinetic character of p-phenyl benzoic acid (PPBA) in developing fetus of rat was investigated by a constant infusion of 14C-PPBA. PPBA level in tissues increased with the day of gestation. The hepatic clearance for PPBA showed the increase with the stage of development. The excretion of the glucuronide from liver into bile increased with the stage, remarkably between the 19th and 21st day of gestation. The developmental profile of UDP-glucuronyltransferase activity in hepatic microsomes of fetus resembled that of the hepatic excretory function for the glucuronide. The glucuronide level in the amniotic fluid increased with the day of gestation, remarkably between the 19th and 21st day of gestation. The elimination rate of the glucuronide from amniotic fluid determined by intraamniotic injection of the glucuronide decreased linearly with the day of gestation.