Diethylene glycol produces nephrotoxic and neurotoxic effects in female rats

Abstract

Context: Diethylene glycol (DEG) is an organic compound found in household products but also as a counterfeit solvent in medicines. DEG poisonings are characterized by acute kidney injury (AKI) and by neurological sequelae such as decreased reflexes or face and limb weakness. Previous studies in male rats have demonstrated that neurotoxic effects develop only with the establishment of AKI, but the dose sensitivity of females to DEG toxicity is unknown.

Objectives: Assessing whether subacute administration of DEG in female rats would delineate any sex-differences in neuropathy or in kidney injury.

Methods: Female Wistar-Han rats were orally administered doses of 4 - 6 g/kg DEG every 12 h and monitored for 7 days. Urine was collected every 12 h and endpoint blood and cerebrospinal fluid (CSF) were collected for renal plasma parameters and total protein estimation, respectively. Motor function tests were conducted before and after treatment. Kidney and brain tissue were analyzed for metabolite content.

Results: Of 12 animals treated with DEG, 3 developed AKI as confirmed by increased BUN and creatinine concentrations. Renal and brain DGA contents were increased in animals that developed AKI compared to animals without AKI. Total CSF protein content in animals with AKI was markedly elevated compared to control and to treated animals without AKI. Decreases in forelimb grip strength and in locomotor and rearing activity were observed in animals with AKI compared to control and to animals without AKI.

Discussion: Repeated dosing with DEG in a female model produced nephrotoxic effects at a dose similar to that in males. The decrease in motor function and increase in CSF protein were only present in females that developed AKI. However, kidney and neurologic effects were assessed only at the end of the treatments, thus limiting determination of which effect occurs first. Limb function and coordination were measured globally and more sensitive tests such as nerve conduction studies might offer a detailed neurotoxicity assessment of the effects of DEG.

Conclusions: These studies show that DEG toxicity does not appear to be sex-specific and that, in males and females, neurological symptoms are present only when DGA accumulation and kidney injury also occur.

Keywords: Diethylene glycol; cerebrospinal fluid; diglycolic acid; female; metabolite toxicity; motor function; nephrotoxicity; neurotoxicity; sex differences.

Figure 1.

Subacute DEG oral administration produced kidney injury in female rats. Kidney injury was assessed by blood urea nitrogen (BUN) (A, top) and plasma creatinine (B, bottom). DEG doses ranged from 4 g/kg to 6 g/kg, administered twice daily. Data are represented as means ± SEM (n=4 for controls, n=3 for animals that developed kidney injury, n=9 for animals that were administered DEG but did not develop kidney injury). Asterisk (*) indicates significant difference from control (one-way ANOVA followed by Bonferroni post hoc test, p<0.05). Pound sign (#) indicates significant difference between DEG-treated animals that did and did not develop kidney injury (one-way ANOVA followed by Bonferroni post hoc test, p<0.05).

Figure 2.

Diglycolic Acid (DGA) concentrations in kidney (A) and brain (B) tissue at termination of study. Data are represented as means ± SEM or range (n=2 for controls, n=2 for animals that developed kidney injury, n=6 for animals that were administered DEG but did not develop kidney injury). Asterisk (*) indicates significant difference from control (one-way ANOVA followed by Bonferroni post hoc test, p<0.05). Pound sign (#) indicates significant difference between DEG-treated animals that did and did not develop kidney injury (one-way ANOVA followed by Bonferroni post hoc test, p<0.05).

Figure 3.

Subacute DEG oral administration produced metabolic acidosis in female rats. Metabolic acidosis was assessed using blood bicarbonate (A, top), and anion gap (B, bottom) at termination of study. Anion gap was calculated as [(Na⁺ + K⁺) – (Cl⁻ + HCO₃⁻)]. Data are represented as means ± SEM (n=4 for controls, n=3 for animals that developed kidney injury, n=9 for animals that were administered DEG but did not develop kidney injury). Asterisk (*) indicates significant difference from control (one-way ANOVA followed by Bonferroni post hoc test, p<0.05). Pound sign (#) indicates significant difference between DEG-treated animals that did and did not develop kidney injury (one-way ANOVA followed by Bonferroni post hoc test, p<0.05).

Figure 4.

Total protein in cerebrospinal fluid of female rats treated with DEG. Data are represented as means ± SEM or range (n=4 for controls, n=2 for animals that developed kidney injury, n=9 for animals that were administered DEG but did not develop kidney injury). Asterisk (*) indicates significant difference from control (one-way ANOVA followed by Bonferroni post hoc test, p<0.05). Pound sign (#) indicates significant difference between DEG-treated animals that did and did not develop kidney injury (one-way ANOVA followed by Bonferroni post hoc test, p<0.05).

Figure 5.

Motor function was altered in female rats treated with DEG that developed kidney injury. Motor function was evaluated by open field total distance traveled (A, top), open field rearing (B, middle), and forelimb grip strength (C, bottom). Data are represented as means ± SEM or range (n=4 for controls, n=2 for animals that developed kidney injury, n=9 for animals that were administered DEG but did not develop kidney injury). Asterisk (*) indicates significant difference from control (one-way (A and B) or two-way (C) ANOVA followed by Bonferroni post hoc test, p<0.05). Pound sign (#) indicates significant difference between DEG-treated animals that did and did not develop kidney injury (one-way (A and B) or two-way (C) ANOVA followed by Bonferroni post hoc test, p<0.05).