Submitted on December 4, 2008
Revised on January 28, 2009
Accepted on February 18, 2009
Strain differences in urinary factors that promote calcium oxalate crystal formation in kidney in ethylene glycol treated rats
Yan Li1 and Kenneth E. McMartin1*
1 LSU Health Sciences Center - Shreveport
* To whom correspondence should be addressed. E-mail: kmcmar{at}lsuhsc.edu.
Ethylene glycol (EG) induced hyperoxaluria is the most commonly employed experimental regimen as an animal model of calcium oxalate (CaOx) stone formation. The variant sensitivity to CaOx among different rat strains has not been fully explored, although the Wistar rat is known to accumulate more CaOx in kidney tissue after low-dose EG exposure than in the F344 rats. Supersaturation of CaOx in tubular fluid contributes to the amount of CaOx crystal formation in the kidney. We hypothesized that the urinary supersaturation of calcium oxalate in Wistar rats is higher than that of F344 rats, thereby allowing for greater CaOx crystal deposition in the Wistar rat. Age-matched male Wistar and F344 rats were treated with 0.75% EG or drinking water for 8 wk. 24-h urine was collected at 0, 2, 4, 6 and 8 wk for analysis of key electrolytes to calculate the CaOx supersaturation. Plasma oxalate level was also measured. Our data confirmed the different sensitivity to renal toxicity from EG between the two rat strains (Wistar > F344). CaOx supersaturation did not differ between the two rat strains before EG treatment. After treatment, plasma oxalate level and urine oxalate excretion were markedly greater in the Wistar rats than in the F344 rats, while urine calcium was slightly decreased in Wistars. Nevertheless, these results led to a higher CaOx supersaturation in urine and greater crystal deposition in kidney in Wistar rats. These studies suggest that during EG treatment, changes in urine electrolytes and in calcium oxalate supersaturation occur to a greater extent in the Wistar rat, in agreement with its greater sensitivity to EG toxicity.
