Urinary oxalate, glycolate, glyoxylate, and citrate after acute intravenous administration of glyoxylate in rats.
OBJECTIVE
Urinary oxalate plays an important role in the formation of calcium oxalate renal stones, and approximately 50% to 60% of urinary oxalate is derived from the endogenous metabolism of glyoxylate. Therefore, we measured urinary oxalate, glycolate, glyoxylate, and citrate concentrations after acute intravenous administration of various doses of glyoxylate in rats to study oxalate metabolism.


METHODS
Male Wistar rats weighing approximately 200 g were divided into six groups of eight animals each. Anesthetized rats received glyoxylate (0, 1, 2, 5, 10, and 20 mg) intravenously. Urine specimens were collected before and every hour after each dose for 4 hours, and the concentrations of oxalate, glycolate, glyoxylate, and citrate were measured by capillary electrophoresis.


RESULTS
Hourly oxalate excretion in the urine peaked at 1 hour after glyoxylate administration, and the peak concentration increased in a dose-dependent manner. Approximately 15% to 30% (mol/mol) of the dose was converted to oxalate within 4 hours and 2% to 4.6% was converted to glycolate. Urinary glyoxylate was not detectable before glyoxylate administration, but large doses resulted in a significant amount of glyoxylate (0.7%-2.3%) appearing in the urine, and the level peaked at 1 hour after administration. Urinary glycolate also peaked at 1 hour after administration of glyoxylate. The urinary citrate concentration generally decreased by 3% to 33% after each dose of glyoxylate, except that it increased slightly after the 20-mg dose.


CONCLUSIONS
Administration of glyoxylate increased urinary oxalate and glycolate excretion in rats, supporting the importance of the glycolate-glyoxylate-oxalate pathway.
Ogawa
Y
Y
Department of Urology, Faculty of Medicine, University of the Ryukyus, Okinawa, Japan. ogawa@med.u-ryukyu.ac.jp
Miyazato
T
T
Morozumi
M
M
Sugaya
K
K
Hatano
T
T
D000818:Animals; D019343:Citric Acid / Q000652:urine*; D004305:Dose-Response Relationship, Drug; D019075:Electrophoresis, Capillary; D006016:Glycolates / Q000652:urine*; D006038:Glyoxylates / Q000008:administration & dosage / Q000494:pharmacology* / Q000652:urine*; D007275:Injections, Intravenous; D008297:Male; D010070:Oxalates / Q000652:urine*; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
D006016:Glycolates; D006038:Glyoxylates; D010070:Oxalates; C031149:glycolic acid; D019343:Citric Acid; C031150:glyoxylic acid