Comparison of glomerular injury in juvenile versus mature rats in a remnant kidney model.

Glomerular compensatory hypertrophy and hypertension (HT) are two factors that have been implicated in the progression of renal disease after nephron loss. Because glomerular compensatory hypertrophy is different in young and mature animals, we studied the effects of 5/6 nephrectomy (RK) in juvenile (5 to 7 weeks of age) and mature (15 to 16 weeks) male Wistar-Kyoto rats to separate the effects of HT from normal growth and glomerular compensatory hypertrophy. The kidneys were perfusion fixed, glomerular pathology was documented, and glomerular diameter and capillary dimensions were determined by standard morphometry. Both groups developed comparable degrees of proteinuria and elevated serum creatinine level when compared with the sham operated controls (SHAM). Although the Wistar-Kyoto rat is "resistant" to the development of HT, 18 of 30 juvenile RK and 3 of 12 mature RK rats developed systolic HT (> or = 150 mm Hg). Acute glomerular necrosis was seen only in the HT rats (9 of 18 juvenile and 2 of 3 mature), whereas glomerular sclerosis was seen in both HT (18 of 18 juvenile and 3 of 3 mature) and normotensive rats (4 of 9 juvenile and 3 of 9 mature). Glomerular diameter was greater in the SHAM mature than SHAM juvenile rats (165 +/- 7 microns vs 142 +/- 12 microns, p < 0.05), but the proportional increase in glomerular diameter after RK was comparable in the juvenile (20%) and mature (19%) RK rats. Increased capillary volume resulting from normal glomerular growth (compare SHAM juvenile with SHAM mature) was due to increased glomerular capillary length (LCP).(ABSTRACT TRUNCATED AT 250 WORDS)