Contribution of phenobarbital antibody-binding capacity to increased serum levels of [3H]phenobarbital

The effect of immunization with protein-sulphanilic acid conjugate on sulphanilic acid disposition in the rat

Rats were immunized with bovine gamma-globulin-sulphanilic acid conjugate and the plasma concentration of sulphanilic acid examined after an intravenous injection of this drug. There was a significant increase in plasma half-life and AUC and a significant decrease in clearance of sulphanilic acid in the immunized rats compared with the control. In the immunized rats, binding of sulphanilic acid to macromolecules in serum, determined by ultrafiltration, decreased with increase of sulphanilic acid concentration. At low concentrations, there was a significant increase in % binding of the drug in the serum of immunized rats compared with controls. There was also a significant reduction in urinary excretion of total drug in the immunized rats compared with controls. These findings suggest that sulphanilic acid-specific antibodies in the serum of immunized animals bind [14C]sulphanilic acid, giving rise to higher serum levels thereby making it unavailable for normal excretory processes.

The effect of immunization with protein-hapten conjugate on the intestinal uptake of p-aminobenzoic acid as a hapten

Intestinal uptake of p-aminobenzoic acid was examined by means of an in vitro everted sac technique in rats immunized with ovalbumin-p-aminobenzoic acid conjugate. A dose-dependent and antigen-specific decrease in the serosal transfer of p-aminobenzoic acid was observed in rats immunized 6 times with protein-hapten conjugate compared with the control. There was a significant increase in the recovery of p-acetamidobenzoic acid, a metabolite of p-aminobenzoic acid, in mucosal fluid, tissue, and serosal fluid in the jejunum. In the case of ileum, increase of p-acetamidobenzoic acid was observed in mucosal fluid. However, there was no significant effect in the ileal p-acetamidobenzoic acid in tissue and serosal fluid between immunized and non-immunized rats. To examine the increased metabolism of immunized rats, N-acetyltransferase activity of the small intestinal mucosa was examined. There was a significant increase in mucosal N-acetyltransferase activity in immunized rats compared with the control animals. These observations suggested that the mucosal immune system may play an important role in regulating the intestinal uptake of the low molecular weight compounds.