Cis-Diamminedichloroplatinum(Ii) Nephrotoxicity: Tubular function after rescue with sodium diethyldithiocarbamate in rats

Sodium diethyldithiocarbamate (DDTC) administered following cis-diamminedichloroplatinum(II) (DDP) has been reported to attenuate structural renal damage and elevation of blood urea nitrogen in rats. Since DDP damages primarily proximal tubular epithelium in this species, we compared proximal tubular function, glomerular function, and histology in male Sprague-Dawley rats treated with DDP followed by either DDTC or 0.9% NaCI solution (NS) rescue. Male Sprague-Dawley rats received a single i.p. injection of DDP (7.5 mg/kg)-mannitol (75 mg/kg)-NaCI (67.5 mg/kg). Forty-five min later, rats were given i.p. injections of either DDTC (750 mg/kg) dissolved in 0.5 ml of NS (DDP + DDTC group; ten rats) or 0.5 ml NS (DDP + NS group; nine rats); additional rats received either DDTC only (DDTC group; six rats) or no treatment (untreated control group; six rats). All groups were sacrificed 5 days later by ether anesthesia and exsanguination. Compared to the untreated control group, the DDTC group had slightly lower mean blood urea nitrogen at sacrifice [12.5 ± 0.5 (S.E.) versus 15.4 ± 0.8 mg/dl; p < 0.025 by unpaired Student's t test]; there was no difference in serum creatinine. The DDP + DDTC group had no diarrhea and no presacrifice deaths in contrast to diarrhea and three presacrifice deaths in the DDP + NS group. Blood urea nitrogen was also lower in the DDP + DDTC group at sacrifice (187 ± 30 versus 383 ± 39 mg/dl; p < 0.005). However, weight loss and serum creatinine were not different. Structural acute tubular necrosis was marked in both DDP groups but was less severe in the DDP + DDTC group than in the DDP + NS group. Proximal tubular function was indexed by the uptake of the organic base N-[¹⁴C]methyl nicotinamide (NMN) and the organic acid p-aminohippurate in renal cortical slices incubated 90 min in Cross and Taggart medium. NMN uptake (expressed as slice to medium ratio) was slightly lower in the DDTC group than in untreated controls (4.1 ± 0.2 versus 5.0 ± 0.2; p < 0.025). Marked depression of p-aminohippurate and NMN uptake occurred in both DDP + DDTC and DDP + NS groups. There was no difference in NMN uptake, but depression of p-aminohippurate uptake was slightly less severe in the DDP + DDTC group (5.3 ± 0.7 versus 3.1 ± 0.3; p < 0.005). We conclude that DDTC rescue attenuates structural DDP injury in this animal model. DDP-mediated proximal tubular dysfunction was only marginally attenuated by DDTC; glomerular filtration rate, as indexed by serum creatinine, was not protected. DDTC attenuation of DDP toxicity may be mediated in part via reducing volume depletion due to DDP-associated diarrhea.