Effect of an acute oral protein load on microalbuminuria in uninephrectomized patients in relation to the time since nephrectomy.

To evaluate the effect of an acute oral protein load (OPL) on urinary albumin excretion (UAE) in uninephrectomized subjects with a negative Albustix test, in relation to the time since nephrectomy, the UAE was determined by a double-antibody 125I radioimmunoassay in 3-hour urine collections before and after 150 g OPL under conditions of moderate physical activity in 18 subjects who underwent unilateral nephrectomy more than 10 years (346.5 +/- 178.60 months) before evaluation and had a mean basal creatinine clearance (CCr) of 45.3 +/- 14 ml/min (group 1), in 21 subjects who underwent unilateral nephrectomy less than 10 years (31.5 +/- 28 months) before evaluation and had a mean basal CCr of 76.0 +/- 22 ml/min (group 2), and in 16 normal volunteers (controls) with a mean basal CCr of 103.1 +/- 12 ml/min. The UAE was higher in group 1 as compared with either group 2 or controls at both basal state (90.8 +/- 65, 19.6 +/- 17, and 11.0 +/- 5 micrograms/min/100 CCr for groups 1 and 2 and controls, respectively; p < 0.001) and after OPL (92.0 +/- 65, 43.6 +/- 24, and 12.0 +/- 5 micrograms/min/100 CCr for groups 1 and 2 and controls, respectively; p < 0.001). However, the increase in UAE following OPL was significant (p < 0.001) only in group 2 patients. In all patients, the basal UAE was negatively correlated with basal CCr (r = 0.63; p < 0.001) and positively correlated with the time since nephrectomy (r = 0.73; p < 0.001) and with both systolic (r = 0.57; p < 0.001) and diastolic blood pressures (r = 0.69; p < 0.001). CCr calculated using 3-hour urine collections increased more in controls (11.2 +/- 44.2%) than in patient groups 1 (1.6 +/- 0.89) and 2 (7.7 +/- 3.7%; p < 0.001). Basal CCr calculated using 24-hour urine collections the day before the test was negatively correlated with the time since nephrectomy in group 1 (r = -0.69; p < 0.001) and positively correlated with the time since nephrectomy in group 2 (r = 0.89; p < 0.001). Multiple regression analysis revealed that the relationship between CCr and duration of uninephric state was independent of age or systolic and diastolic blood pressures in both patient groups. These results suggest that UAE increase significantly after an OPL in subjects who have been nephrectomized less than 10 years before the study and have basal CCr values higher than 50% of normal.(ABSTRACT TRUNCATED AT 250 WORDS)