Vitamin B6 deficiency augments endogenous oxalogenesis after intravenous L-hydroxyproline loading in rats.
The effects of an intravenous hydroxyproline load on endogenous oxalogenesis were compared in rats fed a standard diet or a vitamin B6-deficient diet. Twelve male Wistar rats were randomized to two groups and were fed either a standard diet (control group) or a vitamin B6-deficient diet for 3 weeks. Then the animals were intravenously administered 100 mg (762.6 micromol)/ml hydroxyproline. In the control group, infusion of hydroxyproline increased the 5-h urinary oxalate and glycolate excretion above baseline to 0.27% (2.02 +/- 1.11 micromol) and 0.32% (2.43 +/- 1.60 micromol) of the administered dose (mol/mol), while it was respectively 2.01% (15.24 +/- 2.13 micromol) and 0.00% (-0.02 +/- 0.19 micromol) of the dose in the vitamin B6-deficient group. Therefore, vitamin B6 deficiency augmented endogenous synthesis of oxalate from hydroxyproline by 7.56-fold (15.24/2.02) compared with that in the control group. Urinary citrate excretion was significantly lower at baseline and all other times in the vitamin B6-deficient group compared with the control group. In conclusions, L-hydroxyproline loading augmented endogenous oxalogenesis in the vitamin B6-deficient group without causing hyperglycolic aciduria, and also led to significant hypocitraturia. These findings suggest that hydroxyproline is not metabolized to oxalate via glycolate, but rather via the 4-hydroxyglutamate to glyoxylate pathway (usually requiring vitamin B6-dependent enzymes) even in the presence of vitamin B6 deficiency.
Ogawa
Y
Y
Department of Urology, University of the Ryukyus, 207 Uehara, Nishihara, Okinawa, 903-0215, Japan. ogawa@eve.u-ryukyu.ac.jp
Hossain
R Z
RZ
Ogawa
T
T
Yamakawa
K
K
Yonou
H
H
Oshiro
Y
Y
Hokama
S
S
Morozumi
M
M
Uchida
A
A
Sugaya
K
K
D000818:Animals; D002951:Citrates / Q000652:urine; D006016:Glycolates / Q000652:urine; D006909:Hydroxyproline / Q000008:administration & dosage* / Q000494:pharmacology; D007275:Injections, Intravenous; D008297:Male; D010070:Oxalates / Q000652:urine*; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D026681:Vitamin B 6 Deficiency / Q000652:urine*
D002951:Citrates; D006016:Glycolates; D010070:Oxalates; D006909:Hydroxyproline