In vivo biochemical indices of nephrotoxicity of platinum analogs tetraplatin, CHIP, and cisplatin in the Fischer 344 rat

Abstract

In vivo biochemical indices of nephrotoxicity were investigated in Fischer 344 rats treated with a new platinum analog, tetraplatin [tetrachloro(dl-trans)1,2-diaminocyclohexane platinum(IV), NSC-363812], in comparison with rats receiving equimolar dosages of cisplatin and CHIP [cis-dichloro,trans-dihydroxybis-isopropylamine platinum(IV), NSC-256927]. The goals of this study were to assess the comparative nephrotoxicities and to determine which battery of tests might be useful for the assessment of platinum analog-induced nephrotoxicity in future clinical investigations of these drugs. An iv bolus injection of 6.7, 13.3, 26.7, and 53.3 mumol/kg of each drug in saline was administered and assessment of biochemical parameters was conducted for 15 days postinjection. A combination of urinary enzyme and protein excretion rates along with blood urea nitrogen (BUN) determinations was used to assess the nephrotoxicity of these compounds. At equimolar dosages, tetraplatin appeared to be less nephrotoxic than cisplatin, and CHIP was not nephrotoxic. At all dosages tested, cisplatin increased the rate of urinary excretion of protein, lactate dehydrogenase (LDH), and N-acetylglucosaminidase (NAG) between Days 1 and 5. Tetraplatin did not affect these parameters until the 13.3 mumol/kg dosage. Cisplatin had little effect on the excretion rates of the brush border enzymes alkaline phosphatase and maltase, whereas tetraplatin caused an initial elevation with delayed onset of peak excretion rates at 8 days postinjection. Changes in BUN were not evident until after the 13.3 mumol/kg dosage of cisplatin and the 26.7 mumol/kg dosage of tetraplatin. BUN was useful for ranking the relative toxicities of the three compounds tested, but was not as sensitive in detecting the onset of injury that correlated with early histopathological changes. Tetraplatin appeared to be less nephrotoxic than cisplatin on an equimolar basis and the specific manifestations of its toxicity were different from those observed with cisplatin. Urinary excretion rates for LDH, NAG, and protein proved to be sensitive indicators of platinum analog-induced nephrotoxicity. These indices, combined with BUN determinations and functional assessments, facilitated comparisons of the nephrotoxicity induced by cisplatin and tetraplatin in rats.