Uninephrectomy increases kidney beta2-microglobulin: can it play a role in the progression of kidney damage?

Beta2-microglobulin (beta2M) is highly accumulated by the kidneys of normal rats. The aim of this study was to verify if uninephrectomy can modify the renal uptake of labeled beta2M. For this purpose the radioactivity of plasma and those of the remaining kidney, liver and urine have been measured in uninephrectomized rats (NX) and in controls (C) at different times after the injection as i.v. bolus of 131I-beta2M. The experiments were performed in 114 Sprague-Dawley male rats. Fifty seven animals underwent right nephrectomy, the other animals being the C. NX and their C were divided in 3 groups, studied 2, 4 and 6 weeks after nephrectomy, respectively. Part of the animals were sacrificed 12 min after the injection of labeled beta2M (peak-time, i.e. time of highest kidney accumulation of 131I-beta2M in the normal rat) and part 10 min later. The results demonstrate that: - uninephrectomy increases plasma retention of 131I-beta2M - kidney uptake (total and per gram) is always higher in NX - liver uptake (much lower than that of kidney) is not influenced by uninephrectomy - urine excretion of radioactivity is minimal in both NX and C. The behavior of beta2M is similar to that we previously observed with alpha1-microglobulin and lysozyme. The higher kidney content of some low mw proteins after uninephrectomy could play a role in the progressive reduction of renal function determined by the reduction of renal mass.