Increased levels of DNA synthesis in hyperplastic renal tubules of aging nephropathy in female F344/NCr rats

Histoautoradiography was done to evaluate cell turnover by measuring levels of DNA synthesis in the different anatomic areas of the kidney in aging (76 to 103 weeks of age) female F344/NCr rats after injection of tritiated thymidine (3H-thymidine). All areas showed increased 3H-thymidine labeling indices (LI), including cortical and medullary tubules and interstitium. The extent of increase was directly correlated with increasing severity of the nephropathy. Atrophic, degenerative, and hyperplastic cortical tubules in areas of nephropathy had LI eight to nine times greater than nonaffected areas and more normal kidneys. These observations suggest that the hyperplastic responses of renal tubules to the unknown etiologic agents of aging nephropathy may be similar to those of tubules responding to chemical toxins.