Analysis of factors influencing the in vitro developmental pattern of p-aminohippurate transport by rabbit kidney

Abstract

The ability of rabbit renal cortical tissue to accumulate p-aminohippurate was low at two weeks, increased to a peak at four weeks and then declined to an intermediate value in adult tissue. These differences are not due to differences in the metabolism of p-aminohippurate, tissue composition or tissue viability but reflect real differences in the ability of the tissue to transport or retain p-aminohippurate. The estimated maximal rate of p-aminohippurate transport into slices increased to four weeks and declined whereas runout from tissue was greatest in adult tissue. Both of these changes could contribute to the decline in the slice to medium (S/M) concentration ratio after four weeks. p-Aminohippurate S/M ratio from tissue of all ages was enhanced by acetate. Inasmuch as the p-aminohippurate S/M ratio was greatest in adult tissue in the presence of acetate, the data suggest that the decline normally seen after four weeks reflects the presence of an inhibitor or changes in metabolic requirements in the tissue rather than a decline in intrinsic transport capacity. Preventing contact with solid food during development appeared to retard development of maximal transport capacity. Neomycin was without effect. These data suggest that substances in the diet might serve as substrates to “trigger” the development of anion transport in normal newborn kidneys. Conformation of this suggestion awaits experimental verification.