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

Abstract. 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 seventy 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 obser-vations suggest that the hyperplastic responses of renal tubules to the unknown etiologic agents of aging ne-phropathy may be similar to those of tubules responding to chemical toxins. Age-related renal lesions are common in rats, es-pecially Sprague-Dawley and F344 stocks or strains. I 3, I 4 Aging nephropathy12 has been given a wide variety of names including chronic progressive n e p h r o ~ i s, ~ ~ J ~ , ~ ' spontaneous or chronic n e p h r o ~ i s, ~ , ~ ~ progressive glomer~lonephrosis,~~ ~ glomerulosclerosis,lOJL protein overload nephropathy,21 and old rat nephropathy. l4 Al