Tissue injury and proliferative response induced in rat kidney by cis-diamminedichloroplatinum (II)

Cis-diamminedichloroplatinum (II) (cisplatin), an inorganic platinum salt used in cancer chemotherapy, is characterized by a renal toxicity recognized both in experimental animals and in patients treated with the compound. The purpose of the present study was to explore by both light and electron microscopy the morphological alterations induced in the rat kidney by cisplatin administration and, in particular, to analyse the tissue repair reaction following nephrotoxic injury. Experimental animals (four rats per group) were treated i.p. with 2, 4 or 8 mg/kg cisplatin administered in four consecutive daily injections. The rats were sacrificed 4 days after the last injection. In addition, the persistence of renal lesions and the duration of the repair reaction were determined in rats given 8 mg/kg cisplatin and killed 4, 7, 14 or 21 days after the last injection. The cell proliferation associated with tissue repair was estimated both quantitatively (rate of DNA synthesis) and qualitatively (histoautoradiography and electron microscopy examination) 1 h after in vivo exposure to [3H] thymidine. Renal tissue alterations and the repair reaction were minimal after the administration of 2 or 4 mg/kg cisplatin. In contrast, 8 mg/kg cisplatin caused a spectrum of morphological abnormalities affecting proximal, distal and collecting tubules, and ranging from sublethal cell alterations to tubular necrosis and cystic dilatation. The latter degenerative change primarily involved the straight portion of proximal tubules and seemed to develop over the weeks following cisplatin administration. Concomitantly with the tissue lesions, a burst of cell proliferation, associated with stimulation of DNA synthesis, was apparent in the renal cortex and outer medulla. Whereas a very high incidence of S-phase cells was encountered in seemingly undifferentiated tubules, they also appeared in differentiated proximal, distal and collecting tubules, but were infrequent in cystic tubules. Proliferation of fibroblasts was also stimulated in the renal interstitium. The proliferative response persisted for the whole duration of the experiment, indicating incomplete tissue repair. The long-lasting tubular injury and the slowness of repair are consistent with the chronic renal dysfunction (polyuria and hypomagnesemia) that cisplatin is known to induce in both man and experimental animals.