Epithelial cell proliferation in the rat urinary system induced by parenteral injection of lead salts

In Wistar rats a single intravascular injection of lead nitrate causes substantial cellular proliferation in the proximal tubules of the kidneys and in the epithelium of the renal pelvis, ureters and urinary bladder. The tritiated thymidine labelling index (LI) reaches a peak 18 to 24 h after injection and the mitotic index (MI) increases to a comparable extent 6 to 10 h later. The proliferation is most prominent in the bladder and proximal tubules and is virtually complete at 48 h. After a single intraperitoneal injection the proliferative changes are confined to the ureteric and bladder epithelium. In all affected tissues the proliferation develops without preceding necrosis and appears to be a hyperplastic phenomenon. After intravascular administration the volume of urine and its total protein content are significantly increased and certain proteins were detected which were not present in the urine of saline controls.