Renal Reabsorptive Capacity for α2u-Globulin in the Adult Male Rat

Abstract

Abstract

Adult male rats were maintained on 0, 5, 10, 15, and 20% casein diets to produce a series of animals having serum α2u-globulin levels varying linearly from a normal of 31 μg/ml to a minimum of 13 μg/ml. In this way, it was possible to titrate endogenously the renal reabsorption and urinary excretion of this low molecular weight protein. The average maximal reabsorption rate (T_m) was established to be 9.7 μg/min and was reached at a renal filtered load (F_α2u) of 13.6 μg/min. These data were expressed in terms of a T_m:F_α2u ratio of 0.71. Below this value, the reabsorption declined from 70% to 50% of the F_α2u. Above 0.71, where F_α2u is less than the T_m, the reabsorption increased to 80–90%. It was observed that the fractional renal uptake of the α2u-globulin varied linearly with the filtered load.