DIFFERENT TRANSFERS OF N-ACETYL-P-AMINOBENZOIC ACID AND P-AMINOBENZOIC ACID ACROSS THE PLACENTA AND THE SMALL-INTESTINE IN RATS

The aim of the present study was to evaluate the transfer of N-acetyl- p-aminobenzoic acid (AcPABA) across the rat term placenta and the rat small intestine and to compare it with that of its parent drug p-amino benzoic acid (PABA). Umbilical perfusion of the rat term placenta was used to determine the materno-fetal transfer. AcPABA appeared in the f etal compartment significantly more slowly than PABA (k(transfer) = 0. 023 and 0.064 min(-1), respectively). The rate of equilibration betwee n the maternal and fetal compartments was slightly lower for AcPABA th an for the parent drug (k(equilibration) = 0.0082 and 0.011 min(-1), r espectively). Similarly, AcPABA was shown to be absorbed from the smal l intestine significantly more slowly than PABA (k(a) = 0.052 and 0.82 min(-1); t(max) = 37 and 3.1 min, respectively), Our results showed t hat both investigated compounds which are structurally related and ver y similar in their physical-chemical characteristics crossed both the placental and small intestinal barrier with a different kinetics. AcPA BA was transported across both barriers significantly more slowly than its parent compound, which might indicate a possible equipment of the placenta with a carrier for PABA, a similar one to that previously fo und in the rat small intestine.