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To understand the nephrotoxicity of xenobiotics, the species, strain, sex, and the presence of other chemicals must be considered. This review has considered the importance of these factors in determining the nephrotoxic liability of a drug. For example, cephaloridine is more nephrotoxic in rabbit than rats and is least nephrotoxic in mice. This species-dependent susceptibility to cephaloridine nephrotoxicity appears to be related to the degree in which cephaloridine depletes renal cortical glutathione. Additionally, only male mice of certain strains are susceptible to chloroform-induced nephrotoxicity. Lastly, the presence of certain ketones or ketogenic substances such as acetone and hexane enhance chloroform-induced nephrotoxicity in male Sprague-Dawley rats. Knowing which factors can enhance or limit nephrotoxicity of drugs will lend to a better understanding of the mechanism of these toxicities as well as to design compounds with lesser toxicities.

Metabolism of chloroform (CHCl3) by a cytochrome P-450-dependent process to a reactive metabolite may be required to elicit hepatic and renal toxicities. Specific inducers or inhibitors of cytochrome P-450 have been employed frequently as tools to demonstrate this relationship between metabolism and toxicity in the liver. The experiments reported herein were designed to identify the relationship between metabolism and toxicity of CHCl3 in the kidney of rabbits, a species in which renal cytochrome P-450 is induced by phenobarbital. Pretreatment with phenobarbital enhanced the toxic response of renal cortical slices to CHCl3 in vitro as indicated by decreased p-aminohippurate and tetraethylammonium accumulation. Phenobarbital pretreatment also potentiated in vitro 14CHCl3 metabolism to 14CO2 and covalently bound radioactivity in rabbit renal cortical slices and microsomes. Addition of L-cysteine significantly reduced covalent binding in renal microsomes from both phenobarbital-treated and control rabbits and was associated with the formation of the radioactive phosgene-cysteine conjugate 2-oxothiazolidine-4-carboxylic acid (OTZ). Formation of OTZ was enhanced in renal microsomes from phenobarbital-pretreated rabbits. Thus, this in vitro model supports the hypothesis that the kidney metabolizes CHCl3 to the nephrotoxic metabolite, phosgene.

Renal xenobiotic metabolism can result in production of electrophiles or free radicals that may covalently bind macromolecules or initiate lipid peroxidation. The mechanisms of renal xenobiotic metabolism may vary in different anatomical regions. Kidney cortex contains a cytochrome P-450 system while medulla contains a prostaglandin endoperoxidase. Recently cysteine conjugated-lyase has been implicated in production of reactive intermediates. Metabolic activation may be amplified by accumulation of xenobiotics within renal cells due to tubular concentrating and/or secretory mechanisms. Additionally, renal xenobiotic detoxicification can occur by conjugation with glucuronide, sulfate or glutathione.

Bromobenzene, at doses greater than 5.7 mmol/kg, produced renal proximal tubular necrosis and renal functional changes in mice. p-Bromophenol and o-bromophenol were the major urinary phenolic bromobenzene metabolites although m-bromophenol and 4-bromocatechol were also excreted in detectable quantities. With the exception of o-bromophenol, urinary metabolites were excreted primarily as conjugates. 4-Bromocatechol and the 3 bromophenol isomers were nephrotoxicants (measured as increased blood urea nitrogen and decreased accumulation of organic anions by renal cortical slices) but not hepatotoxicants (measured as serum glutamic pyruvate transaminase) in vivo at 0.56 mmol/kg (i.v.). Preincubation of renal cortical slices with each of these bromobenzene metabolites for 90 min resulted in dose-dependent decreases in the accumulation of p-aminohippurate and tetraethylammonium. At 10 mumol/preincubation (2.4 mM), organic ion accumulation was decreased maximally by all bromobenzene metabolites examined while equimolar amounts of bromobenzene were without effect. 4-Bromocatechol was the most potent nephrotoxicant in vitro. Administration of 0.53-2.12 mmol/kg (i.v.) 4-bromocatechol to mice resulted in a dose-dependent decrease in renal function while hepatic function was altered only slightly at the higher doses. The renal cortical necrosis produced by in vivo administration of 4-bromocatechol could not be distinguished histologically from that induced by bromobenzene. These results demonstrate that 4-bromocatechol and the 3 bromophenol isomers are nephrotoxicants that can be generated from bromobenzene in mice.

Worldwide industrialization and environmental pollution have increased the incidence of human exposure to halogenated aliphatic hydrocarbons, many of which are injurious to the mammalian kidney. Evaluation of human risk from haloalkane exposure requires knowledge about the mechanisms of the nephrotoxic effects of these agents so that appropriate animal models of human response can be developed. Recent studies indicate that nephropathy following methoxyflurane (2,2-dichloro-1,1-difluoroethyl methyl ether) anesthesia is caused by hepatic enzymatic release of inorganic fluoride ion, a nephrotoxic component of the parent molecule. Thus, the toxic effect is dependent upon hepatic metabolism of methoxyflurance. Acute chloroform injury to the kidney also may be caused by a toxic metabolite. In this case, however, the metabolite is most likely produced within the kidney. Chloride ion is relatively innocuous, suggesting that a carbon fragment of chloroform is the nephrotoxic agent. These results indicate that haloalkane metabolism, both renal and hepatic, can be important determinants of haloalkane nephropathy.

Strain differences in susceptibility of rats to acetaminophen (APAP)-induced nephrotoxicity have been previously reported. Young adult male Fischer-344 (F-344) rats are susceptible whereas weight-matched Sprague-Dawley (SD) rats are not susceptible to APAP nephrotoxicity. The present study was designed to evaluate the role of pharmacokinetics in strain-dependent APAP nephrotoxicity. Age-matched (2-month-old) male F-344 and SD rats received 250-750 mg APAP/kg, i.v., or 0-1000 mg APAP/kg, i.p. Pharmacokinetic variables were evaluated following i.v. APAP and 24 h urinary excretion of APAP and major metabolites was determined following both i.v. and i.p. administration of APAP. Following i.p. administration, nephrotoxicity was observed only in F-344 rats following 1000 mg APAP/kg; SD rats were not susceptible to APAP-induced nephrotoxicity. In contrast, nephrotoxicity did not occur in either F-344 or SD rats administered APAP i.v. Pharmacokinetic variables (volume of distribution, apparent systemic clearance, and apparent terminal half-life) of APAP were similar in F-344 and SD rats. No striking differences in the pattern of specific urinary metabolites were observed between F-344 and SD rats treated with i.p. or i.v. APAP. Thus, strain differences in APAP-induced nephrotoxicity do not appear to be due to differences in pharmacokinetics or major pathways of APAP metabolism.

These studies were initiated to determine (1) if cisplatin (cis-DDP)-induced hyperglucagonemia is related to decreased hormone degradation, (2) the relationship between impaired kidney function associated with cis-DDP nephrotoxicity and hyperglucagonemia, and (3) the contribution of cis-DDP-induced hyperglucagonemia to disturbances in glucose metabolism in male F-344 rats. Administration of 5 or 7.5, but not 2.5, mg/kg cis-DDP iv increased fasting plasma immunoreactive glucagon (IRG) concentrations. Hyperglucagonemia following cis-DDP treatment was characterized by an increase in the biologically active or true pancreatic form of IRG as well as an increase in an extrapancreatic component. cis-DDP treatment (5 mg/kg) resulted in a prolonged half-life and a reduced rate of plasma disappearance of exogenous glucagon. Reducing cis-DDP nephrotoxicity, via mannitol pretreatment, resulted in a significant reduction in total, true pancreatic, and extrapancreatic plasma IRG. Other nephrotoxicants, such as glycerol or gentamicin, also resulted in hyperglucagonemia, indicating that the effects of cis-DDP on glucagon metabolism are also characteristic of other nephrotoxicants and, therefore, may be secondary to kidney toxicity. Despite marked hyperglucagonemia following cis-DDP treatment, neither severe fasting hyperglycemia nor increased hepatic and renal gluconeogenic enzyme activity was apparent in treated animals. This apparent discrepancy cannot be attributed to glucagon resistance at the target tissue level since cis-DDP-treated animals responded appropriately to exogenous glucagon. These results indicate that hyperglucagonemia following cis-DDP treatment (1) may be related to decreased glucagon degradation associated with impaired renal function and (2) does not markedly disrupt glucose homeostasis.

Chronic progressive nephropathy is a spontaneous disease common among aging laboratory rats, often making it difficult to distinguish age-related from drug-related effects in chronic toxicity studies. Morphological changes of the kidney that occur with age include thickening of glomerular and proximal tubular basement membranes, mesangial proliferation, fusion of foot processes, and, ultimately, glomerular sclerosis. Proteinuria (specifically, albuminuria) is the most striking characteristic change in renal function of aging rats and, generally, correlates well with the severity of age-related glomerular pathology. Changes in tubular functions also may occur with aging but have not been investigated sufficiently. The pathogenesis of chronic progressive nephropathy is not known; however, hemodynamic adaptations after ad libitum consumption of protein-rich diets may be a contributing factor. High-protein diets increase glomerular pressures and flows, perhaps facilitating excretion of metabolic end products. These hemodynamic adaptations may impair the permselective properties of the glomerulus, leading to: enhanced accumulation of macromolecules in the mesangium, progressive mesangial expansion, and, ultimately, glomerular sclerosis. Indeed, decreasing total food or protein intake retards or prevents the progression of age-related nephropathy. Inasmuch as chronic toxicity studies are complicated by a high incidence of spontaneous nephropathy, implementation of a restricted dietary regimen may improve detection of drug-induced toxicity.

Four consecutive intraperitoneal (i.p.) injections with 40 mg/kg of 1,2-dibromo-3-chloropropane (DBCP) reduced the in vitro accumulation of p-aminohippurate (PAH) and tetraethylammonium (TEA) by slices of renal cortex and increased blood urea nitrogen (BUN) concentration in both male and female rats, but elevated serum glutamic pyruvic transaminase (GPT) and glutamic oxaloacetic transaminase (GOT) activities in females only. Four consecutive treatments with 1,2-dibromoethane (EDB) reduced the accumulation of PAH in male rats, but failed to alter TEA accumulation, BUN concentration or GPT and GOT activities in rats of either sex. Single i.p. injections of EDB or DBCP (40 mg/kg, approximately one-half of the acute, i.p. LD50 values) were without effect on serum GPT and GOT activities, BUN concentration or the accumulations of PAH and TEA in male rats when measured 24, 48 or 96 h after treatment, except that PAH accumulation was reduced at 96 h. These results indicate that BUN and the accumulations in vitro of PAH and TEA by renal cortical slices are appropriate endpoints for studying DBCP nephrotoxicity. Measurements of serum GOT and GPT activities detected DBCP hepatotoxicity in female rats only. The nephrotoxicity of EDB was indicated by measurement of TEA accumulation only.

Acetaminophen (APAP) produces renal necrosis restricted to the straight segment of the proximal tubule in Fischer 344 (F344) rats. On the other hand, Sprague-Dawley (SD) rats are extremely resistant to the nephrotoxic effects of APAP. Such strain differences may be due to different susceptibilities to the nephrotoxic metabolite, p-aminophenol (PAP). PAP administration in both strains of rats resulted in a renal lesion indistinguishable from the APAP-induced renal lesion in F344 rats. The PAP-induced renal lesions in F344 rats, however, were generally more severe than those in SD rats. PAP-induced renal functional changes (elevation in blood urea nitrogen and reduction in the accumulation of p-aminohippurate by renal cortical slices) correlated with strain-dependent histopathological changes. Analysis of urinary metabolites over a 24-hr period following PAP administration (200 and 400 mg/kg) indicated that more PAP was excreted as APAP in SD than in F344 rats. Covalent binding of PAP to renal microsomes in vitro was much greater in F344 rats than in SD rats at substrate concentrations less than 5 mM. These results suggest that strain differences in PAP-induced nephrotoxicity may be related to differences in the intrarenal activation of PAP. Furthermore, strain differences in APAP-induced nephrotoxicity may be related to strain differences in the activation of the nephrotoxic metabolite, PAP.

Acetaminophen (APAP) produced renal necrosis restricted to the straight segment of the proximal tubule in Fischer 344 (F344) rats but not in Sprague-Dawley (SD) rats. APAP-induced renal functional changes (elevation in blood urea nitrogen and reduction in the accumulation of p-aminohippurate by renal cortical slices) also correlated with strain-dependent histopathological changes. Such strain differences have been attributed to differences in renal P-450 activation of APAP or the deacetylation of APAP to the nephrotoxic metabolite, p-aminophenol (PAP). Kidneys from F344 rats displayed greater concentrations of P-450 and greater ethoxycoumarin-o-deethylase activity than kidneys from SD rats. However, covalent binding of [ring-14C]APAP to renal and hepatic microsomal protein in vitro was similar for both SD and F344 rats. Deacetylation of APAP to PAP was similar in renal and hepatic homogenates from SD and F344 rats. Furthermore, isolated kidneys from SD and F344 rats perfused with APAP excreted PAP at similar rates. PAP excretion, over a 24-hr period following APAP administration, was greater in F344 rats than in SD rats only at the highest dose (900 mg/kg) of APAP. Thus, strain differences in APAP-induced nephrotoxicity apparently cannot be attributed to differences in P-450 activation of APAP or in deacetylation to the nephrotoxic metabolite, PAP.

Renal cortical necrosis induced by acetaminophen (APAP) may be related to generation of reactive intermediates by two mechanisms of metabolic activation, direct P-450 dependent metabolic activation (P-450) or metabolic activation subsequent to deacetylation of APAP to p-aminophenol (PAP). Generation of arylating intermediates by both pathways of metabolic activation was quantified in cyclohexamide (HEX)-pretreated or naive rats in vivo with specifically labeled [14C]APAP. The association of each type of metabolic activation with APAP-induced nephrotoxicity was determined in Fischer 344 (F344) and Sprague-Dawley (SD) rats, strains that are susceptible and resistant to APAP-induced nephrotoxicity, respectively. Covalent binding of [ring-14C]APAP to renal cortex was approximately four times greater than [acetyl-14C]APAP in HEX-pretreated F344 rats. In contrast, in SD rats pretreated with HEX covalent binding of [ring-14C]APAP and [acetyl-14C]APAP in the renal cortex was not different. Furthermore, covalent binding of [ring-14C]APAP to renal cortical protein was approximately four times greater in F344 rats than in SD rats. Arylation of hepatic protein by either [ring-14C]APAP or [acetyl-14C]APAP was similar regardless of strain or pretreatment regimen. These studies demonstrated arylation of renal macromolecules in vivo by reactive intermediates resulting from PAP in F344 but not SD rats. Since F344, but not SD, rats are susceptible to APAP-induced nephrotoxicity, it appears the formation of arylating intermediates by PAP is a requisite step in APAP-induced nephrotoxicity.

Large doses of the cephalosporin antibiotic, cephaloridine, produce acute proximal tubular necrosis in humans and in laboratory animals. Cephaloridine is actively transported into the proximal tubular cell by an organic anion transport system while transport across the lumenal membrane into tubular fluid appears restricted. High intracellular concentrations of cephaloridine are attained in the proximal tubular cell which are critical to the development of nephrotoxicity. There is substantial evidence indicating that oxidative stress plays a major role in cephaloridine nephrotoxicity. Cephaloridine depletes reduced glutathione, increases oxidized glutathione and induces lipid peroxidation in renal cortical tissue. The molecular mechanisms mediating cephaloridine-induced oxidative stress are not well understood. Inhibition in gluconeogenesis is a relatively early biochemical effect of cephaloridine and is independent of lipid peroxidation. Furthermore, cephaloridine inhibits gluconeogenesis in both target (kidney) and non-target (liver) organs of cephaloridine toxicity. Since glucose is not a major fuel of proximal tubular cells, it is unlikely that cephaloridine-induced tubular necrosis is mediated by the effects of this drug on glucose synthesis.