Studies of the specificity of an antibody directed against probenecid. Investigations with probenecid analogs

An antibody against probenecid was obtained in rabbits immunized with probenecid conjugated to bovine serum albumin. The antibody exhibited a high degree of specificity (competitive assay) as shown by studies with 25 analogs which included isomers, homologs and metabolites. Interestingly, three analogs (2′-hydroxy, glycine and methyl ester) had a higher affinity than probenecid. The side-chain metabolites all had much lower affinity than the parent drug. Radioimmunoassay was carried out with dextran-coated charcoal and was sensitive to about 1 nanogram. This raises the possibility of radioimmunoassay of probenecid in plasma and tissue.     

Statistical-mechanical theory of passive transport through semipermeable membranes.

The first general multicomponent equations for transport through semipermeable membranes are derived from basic statistical-mechanical principles. The procedure follows that used earlier for open membranes, but semipermeability is modelled mathematically by the introduction of external forces on the impermeant species. Gases are treated first in order to clarify the problems involved, but the final results apply to general nonideal solutions of any concentration. The mixed-solvent effect is treated rigorously, and a mixed-solvent osmotic pressure is defined. A useful specific identification of so-called osmotic flow is given, along with a demonstration that such an identification cannot be unique. Results are obtained both for discontinuous membrane models, and for a continuous model.