Abstract

BACKGROUND
Nitric oxide synthase (NOS) has been suggested to have a role in renal injury of aging rats.
METHODS
Renal function and histology were compared between 12 month-and 7-9 week-old rats. Proliferating activity and cell death were evaluated by PCNA index and apoptosis. Three isoforms of NOS (eNOS, iNOS, and nNOS) were stained by immunohistochemistry.
RESULTS
Serum creatinine level was increased in old rats (1.0 mg/dL vs 0.5 mg/dL, p=0.000). 24 h proteinuria and urinary NO were comparable between the two groups. The percentage of global and segmental glomerulosclerosis increased in old rats. PCNA index decreased in the glomeruli (0.1 vs 0.6/glomerulus, p=0.005) and the tubulointerstitium (10.2 vs 19.2/mm2, p=0.019) of old rats compared to that of young rats. However, no difference was observed in the number of TUNEL positive cells. eNOS was not stained in young and old rat kidney, whereas iNOS was stained in the interstitial inflammatory cells of old rats (0.3 vs 0.0 of young rats/mm2, p=0.188). Macula densa nNOS staining significantly decreased in old rats compared to young rats (5.6 vs 9.5/mm2, p=0.009).
CONCLUSIONS
Proliferating activity is more affected than cell death with aging. Decreased nNOS expression without alteration of eNOS and iNOS expressions may implicate nNOS as a marker of renal injury in the early stage of aging.

• Keywords: Kidney;Aging;Histology;Nitric Oxide Synthase