Occurrence of C 14 -Oxalate in Rat Urine after Administration of C 14 -Tryptophan. ∗

Abstract

Studies from this laboratory have indicated that there is an increase in endogenous oxalate excretion in Vit. B₆ deficiency(1,2). Following administration of tryptophan load tests to human subjects, Gershoff and Prien (3), Farvar et al(4), and Faber et al(5), have reported increased excretion of oxalate. In the present study the effect of tryptophan on excretion of oxalate by Vit. B₆-deficient and control rats has been investigated.

Methods. Two groups of 18 male weanling Charles River CD rats were fed a purified diet ad libitum with or without Vit. B₆ consisting of: casein, 15%; sucrose, 75.7%; corn oil, 4%; salts IV(6), 4%; cod liver oil, 1%; and choline, 0.3%. Four mg of thiamine hydrochloride, 8 mg of riboflavin, 40 mg of niacin, 20 mg of calcium pantothenate, 1 mg of folic acid, 1 mg of menadione, 0.2 mg of biotin, 0.05 mg of Vit. B₁₂ and, when used, 4 mg of pyridoxine hydrochloride, were added to each kilo of diet. After 3 weeks the rats were injected intraperitoneally with 5 μc of either DL tryptophan 2-C¹⁴ or DL tryptophan 3-C¹⁴ per 100 g of body weight.

The rats were placed in metabolic cages in groups of 3 and 48-hour urine collections were made. Oxalates were extracted and precipitated from the urines as described by Powers and Levatin(7). The calcium oxalate precipitate was dissolved in 1 ml of 20% sulfuric acid and 0.5 ml of 1% manganous sulfate and transferred to a Warburg flask. One ml of 0.03 n potassium permanganate was added from the side arm and the flasks were shaken for 30 minutes. The CO₂ evolved was trapped in the center well on filter paper wet with KOH and the radioactivity determined in a liquid scintillation counter as described by Buhler(8).