Proliferative response of renal pelvic epithelium in rats to oral administration of ortho-phenylphenol, sodium ortho-phenylphenate and diphenyl.

Changes in DNA synthesis levels and morphology as observed by scanning electron microscopy (SEM) and light microscopy in rat renal papilla and pelvis following oral administration of ortho-phenylphenol (OPP), sodium ortho-phenylphenate (OPP-Na) and diphenyl, were investigated in F344 rats. OPP and OPP-Na treatment for 4 weeks was associated with elevated DNA synthesis in both renal papilla and pelvis, in addition to distinct morphological cell surface alterations. Sequential light microscope observation revealed induction of renal papillary necrosis from week 4, followed by regeneration hyperplasia at weeks 16 and 24, but no changes in the renal pelvis in the OPP case. OPP-Na not only similarly affected the renal papilla, but also brought about development of hyperplasia in the renal pelvis. No proliferative response of the kidney was apparent in rats fed diphenyl. The present study indicated that the proliferative responses in the renal pelvic epithelium following OPP-Na are similar to those induced by this chemical in the urinary bladder, and that in both cases they are indicative of promoting or carcinogenic potential.