Automated determination of red cell methaemoglobin reductase activity by a continuous-flow system for screening hereditary methaemoglobinaemia.

Tanishima, Kiyoh; Fukuda, Nahoko; Takeshita, M; Takizawa, Yoshio; Kitamura, Tsuneo; Yoneyama, Yoshimasa

doi:10.1136/jcp.32.6.584

Cited by 3 publications

(3 citation statements)

References 14 publications

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“…Experiments that use whole blood with intact erythrocytes are needed to determine the physiological relevance of either of these processes to rates of methemoglobin reduction. However, reported cytb 5 r activities are most commonly measured indirectly by spectrophotometric measurement of the enzyme's reduction of ferrocyanide-methemoglobin complex or NADH-ferricyanide in hemolysates as alternative substrates for methemoglobin (3,42). Alternatively, cytb 5 r activities have been studied in whole blood, but with the use of dilute suspensions of red blood cells washed after pharmacological induction of methemoglobinemia with hemoglobin-oxidizing agents (2,40).…”

mentioning

confidence: 99%

A novel method of measuring reduction of nitrite-induced methemoglobin applied to fetal and adult blood of humans and sheep

Power¹,

Bragg²,

Oshiro³

et al. 2007

Journal of Applied Physiology

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The reaction of nitrite with deoxyhemoglobin results in the production of nitric oxide and methemoglobin, a reaction recently proposed as an important oxygen-sensitive source of vasoactive nitric oxide during hypoxic and anoxic stress, with several animal studies suggesting that nitrite may have therapeutic potential. Accumulation of toxic levels of methemoglobin is suppressed by reductase enzymes present within the erythrocyte. Using a novel method of measuring methemoglobin reductase activity in intact erythrocytes, we compared fetal and adult sheep and human blood. After nitrite-induced production of 20% methemoglobin, the blood was equilibrated with carbon monoxide, which effectively stopped further production. Methemoglobin disappearance was first order in nature with specific rate constants (k x 1,000) of 12.9 +/- 1.3 min(-1) for fetal sheep, 5.88 +/- 0.26 min(-1) for adult sheep, 4.27 +/- 0.34 for adult humans, and 3.30 +/- 0.15 for newborn cord blood, all statistically different from one another. The effects of oxygen tensions, pH, hemolysis, and methylene blue are reported. Studies of temperature dependence indicated an activation energy of 8,620 +/- 1,060 calories/mol (2.06 kJ/mol), appreciably higher than would be characteristic of processes limited by passive membrane diffusion. In conclusion, the novel methodology permits absolute quantification of the reduction of nitrite-induced methemoglobin in whole blood.

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mentioning

confidence: 99%

A novel method of measuring reduction of nitrite-induced methemoglobin applied to fetal and adult blood of humans and sheep

Power¹,

Bragg²,

Oshiro³

et al. 2007

Journal of Applied Physiology

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“…This condition is caused by deficiencies in the cytochrome b5 reductase enzyme, with two distinct, previously described forms of methemoglobinemia (I and II) 7,11,13,15 . Type I is a benign form caused by a deficiency in the soluble erythrocyte form of the enzyme, typically due to amino acid substitutions that result in protein instability.…”

Section: Discussionmentioning

confidence: 99%

“…A soluble form of these proteins in the erythrocytes is responsible for reducing MetHb back into functional hemoglobin. Several studies have demonstrated that methemoglobinemia is associated with genetic variations in both CYB5A and CYB5R3 , resulting in decreased enzyme activity 7,11–15 .…”

Section: Introductionmentioning

confidence: 99%

Genetic variation in CYB5R3 is associated with methemoglobin levels in preterm infants receiving nitric oxide therapy

et al. 2014

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Background In recent years, increasing numbers of preterm infants have been exposed to inhaled nitric oxide (iNO). This population has decreased methemoglobin (MetHb) reductase activity in their erythrocytes, which may increase the risk of MetHb toxicity. We sought to determine if genetic factors are associated with the observed variance in MetHb levels. Methods A population of 127 preterm infants was genotyped for five single-nucleotide polymorphisms (SNPs) in the CYB5A and CYB5R3 genes. iNO dose and levels of MetHb were obtained by chart abstraction. Analysis of variance was performed to identify genetic associations with MetHb levels. Results An association was found between the heterozygous genotype (GA) of rs916321 in the CYB5R3 gene and the mean of the first recorded MetHb levels in Caucasian infants (p=0.01). This result remained significant after adjustment for the iNO dose (p=0.009), gender (p=0.03), multiple gestation (p=0.03), birth weight (p=0.02), and gestational age (p=0.02). No significant associations were found with the other SNPs. Conclusion We demonstrate a novel genetic association with neonatal MetHb levels. Identification of genetic risk factors may be useful in determining which preterm infants are most at risk of developing MetHb toxicity with the use of iNO.

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A simple enzymatic microdetermination of cytochrome b5 in erythrocytes

Takeshita

Yubisui

Tanishima

et al. 1980

Analytical Biochemistry

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Automated determination of red cell methaemoglobin reductase activity by a continuous-flow system for screening hereditary methaemoglobinaemia.

Cited by 3 publications

References 14 publications

A novel method of measuring reduction of nitrite-induced methemoglobin applied to fetal and adult blood of humans and sheep

A novel method of measuring reduction of nitrite-induced methemoglobin applied to fetal and adult blood of humans and sheep

Genetic variation in CYB5R3 is associated with methemoglobin levels in preterm infants receiving nitric oxide therapy

A simple enzymatic microdetermination of cytochrome b5 in erythrocytes

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