Study of a rat model for calcium oxalate crystal formation without severe renal damage in selected conditions.
BACKGROUND
Although nephrotoxic in high doses, ethylene glycol (EG) has been used with ammonium chloride (NH(4)Cl) or vitamin D(3) to study calcium oxalate stone formation in rat models. In the present study we used EG alone or with NH(4)Cl to study hyperoxaluria, crystaluria, and crystal attachment to renal epithelial cells in rats with minimal renal damage.


METHODS
Six-week-old male Sprague-Dawley (SD) rats were given food and special drinking water. In experiment 1 the drinking water contained 1.0% NH(4)Cl plus four different concentrations of EG (0.8%, 0.4%, 0.2%, 0.1%). In experiment 2 the drinking water contained EG alone (0.8%, 0.4%, 0.2%, 0.1%). Urine was collected for 24 h before the rats were sacrificed. In experiment 1 the rats were sacrificed 5-13 days after starting the special water. In experiment 2 the rats were sacrificed 7-21 days after starting the special water. Bladder urine was also obtained. Blood and urine were tested for calcium, phosphorus, and creatinine. In addition, urine was tested for pH, oxalate and N-acetyl-beta-D glucosaminidase (NAG). Kidney sections were stained with hematoxylin-eosin, von Kossa and Pizzolato stain. Crystal morphology was determined using polarizing microscopy, and composition was determined using high-resolution X-ray powder diffraction.


RESULTS
Experiment 1: Aggravation of renal function, an increase in urinary oxalate and NAG excretion, and crystals observed in the kidneys all correlated with EG concentration and length of drinking time. In bladder urine, calcium oxalate monohydrate (COM) crystals exceeded calcium oxalate dihydrate (COD) crystals. Experiment 2: Renal function remained unchanged. Oxalate excretion increased and NAG increased slightly. Crystals occurred only in the papillary tip region. Crystals in bladder urine were mostly COD.


CONCLUSIONS
In the current rat model, calcium oxalate crystaluria could be induced without severe renal damage in selected cases. Either and/or both COM and COD might form and interact with kidney epithelium. We propose different experimental conditions to study the various phases of calcium oxalate stone formation in young male SD rats.
Yamaguchi
Satoshi
S
Department of Medicine, Medical College of Wisconsin and the Department of Veterans Affairs Medical Center, Milwaukee, Wisconsin, USA. syama@asahikawa-med.ac.jp
Wiessner
John H
JH
Hasegawa
Andrew T
AT
Hung
Linda Y
LY
Mandel
Gretchen S
GS
Mandel
Neil S
NS
D000118:Acetylglucosaminidase / Q000652:urine; D000643:Ammonium Chloride / Q000009:adverse effects; D000818:Animals; D002129:Calcium Oxalate / Q000378:metabolism / Q000652:urine*; D003460:Crystallization; D004195:Disease Models, Animal; D004847:Epithelial Cells / Q000187:drug effects*; D019855:Ethylene Glycol / Q000009:adverse effects; D006959:Hyperoxaluria / Q000150:complications*; D007668:Kidney / Q000166:cytology / Q000473:pathology; D007669:Kidney Calculi / Q000139:chemically induced / Q000150:complications / Q000503:physiopathology*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley
D000643:Ammonium Chloride; D002129:Calcium Oxalate; D000118:Acetylglucosaminidase; D019855:Ethylene Glycol