Effects of dietary protein and captopril on glomerular permselectivity in rats with unilateral nephrectomy

Proteinuria and progressive glomerulosclerosis are commonly associated with nephron loss. We studied the pathogenesis of these lesions by examining the role of changes in specific glomerular capillary wall permeability properties in uninephrectomized rats. The development of altered capillary permselectivity to macromolecules and loss of glomerular basement membrane anionic charge were measured by the dextran fractional clearance and ferritin tracer probe methods, respectively. In addition, the protective effect of dietary protein restriction and an angiotensin I-converting enzyme inhibitor (captopril) were studied in eight groups of male Sprague-Dawley rats. Four groups of rats underwent sham-nephrectomy or left nephrectomy and were fed an 8.5% protein diet (sham-nephrectomy and low protein, nephrectomy and low protein) or a 30% protein diet, respectively (sham-nephrectomy and high protein, nephrectomy a high protein). Four other groups of rats underwent sham-nephrectomy or left nephrectomy and were treated with captopril (50 mg/kg/day) while receiving a 8.5% protein diet (sham-nephrectomy, low protein and captopril, nephrectomy, low protein and captopril) or a 30% protein diet, respectively (sham-nephrectomy, high protein and captopril, nephrectomy, high protein and captopril). Rats were nephrectomized at 21 days of age and were functionally tested and sacrificed at 7 months of age. The nephrectomy and high protein rats had significantly greater proteinuria and higher fractional clearance of neutral dextrans in the 30 to 42 A range compared with that of sham-nephrectomy and high protein, nephrectomy and low protein, and nephrectomy, high protein and captopril rats. The nephrectomy and high protein rats also had a significantly lower labeling of the glomerular basement membrane with cationic ferritin tracer molecules compared with the nephrectomy and low protein and nephrectomy, high protein and captopril rats. Of the eight treatment groups, the nephrectomy and high protein rats had the most severe glomerular lesions. In general, nephrectomized rats fed low dietary protein and nephrectomized rats treated with captopril had significantly less proteinuria, glomerular lesions, and milder changes in the glomerular capillary wall porosity and glomerular basement membrane anionic charge.(ABSTRACT TRUNCATED AT 400 WORDS)