Nephrology Dialysis Transplantation, Vol 12, Issue 8 1622-1628, Copyright © 1997 by Oxford University Press
K Koyama, A Yoshida, A Takeda, K Morozumi, T Fujinami and N Tanaka
Background: We previously investigated the factors
involved in uraemic neuropathy in patients undergoing regular haemodialysis
and found a significant relationship between the severity of vibration
sensation impairment and the patients' smoking habits. The administration
of methylcobalamin markedly improved the severity of uraemic neuropathy in
terms of vibration perception thresholds. We presumed that abnormal cyanide
metabolism is involved in the development of uraemic neuropathy.
Method: Serum levels of thiocyanate
(SCN-), the detoxication product of cyanide, were
determined in 12 patients with preterminal chromic renal failure (PCRF), 30
patients undergoing regular haemodialysis (HD patients), and 13 healthy
volunteers as a control group. Nine of the 30 HD patients were smokers. In
addition, in 10 HD patients without smoking habits and 10 non-smoking
healthy volunteers, the proportion of each vitamin B12 analogue in total
vitamin B12 was estimated. Results: The mean serum
SCN- level of the 12 PCRF patients
(5.1±1.5 &mgr;g/ml) was significantly higher than that of
the control (2.8±0.9 &mgr;g/ml) (p<0.01). The mean
SCN- level before haemodialysis in the 21
non-smoking HD patients was identical to that in the PCRF group, whereas
the level in the nine smoking HD patients (7.2±1,8
&mgr;g/ml) significantly higher than that in the non-smoking subgroup
(P<0.01). In 16 HD patients with methylcobalamin treatment, serum
SCN- levels were lower than in those without
methyl-cobalamin treatment (4.5±0.5 &mgr;g/ml in non-smoking
subgroup, P<0.05). And in the methylcobalamin-treated subgroup
(n=5), the proportion of each vitamin B12 analogue in total vitamin B12 was
normal. In the untreated subgroup (n=5), the proportion of cyanocobalamin
fraction (10.5±2.6%) was as high as the level in Leber's disease
patients, while the proportion of methylcobalamin fraction was low. And the
serum cyanocobalamin level was higher in the treated subgroup.
Conclusion: In uraemic patients, cyanide detoxication
capability is impaired because of a reduced SCN-
clearance, and increased cyanocobalamin synthesis indicates elevation of
cyanide pool, which would be related to the development of uraemic
neuropathy. Methylcobalamin was considered to be utilized in cyanide
detoxication process via cyanocobalamin synthesis.
Keywords: chronic renal failure; uraemic neuropathy;
cyanide; vitamin B12; haemodialysis
ORIGINAL ARTICLES
Abnormal cyanide metabolism in uraemic patients
Division of Nephrology, Nagoya Daini Red Cross Hospital, 2-9, Myoken-cho, Showa-ku, Nagoya 466, Japan; Third Department of Internal Medicine, Nagoya City University Medical School, Nagoya, Japan; Department of Internal Medicine, Aoto-Hospital Jikeikai University School of Medicine, Tokyo, Japan; Corresponding author
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