Hydrogen transfer between C19 steroids during oxidoreduction at C-17 in vivo

Cronholm, Tomas; Rudqvist, Ulf

doi:10.1016/0005-2760(82)90021-2

Cited by 6 publications

(1 citation statement)

References 23 publications

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“…Intermolecular hydrogen transfer during oxidoreduction in vivo has been previously demonstrated for C1 9-steroid sulphates by a method similar to the one used in the present study (Cronholm & Rudqvist, 1982). Oxidoreduction may also be detected by the decrease in 3H/14C ratio of a substrate labelled with 14C and 3H at the hydroxylated carbon.…”

Section: The Methodssupporting

confidence: 72%

Hydrogen transfer between ethanol molecules during oxidoreduction in vivo

Cronholm¹

1985

Biochemical Journal

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Rates of exchange catalysed by alcohol dehydrogenase were determined in vivo in order to find rate-limiting steps in ethanol metabolism. Mixtures of [1,1-2H2]- and [2,2,2-2H3]ethanol were injected in rats with bile fistulas. The concentrations in bile of ethanols having different numbers of 2H atoms were determined by g.l.c.-m.s. after the addition of [2H6]ethanol as internal standard and formation of the 3,5-dinitrobenzoates. Extensive formation of [2H4]ethanol indicated that acetaldehyde formed from [2,2,2-2H3]ethanol was reduced to ethanol and that NADH used in this reduction was partly derived from oxidation of [1,1-2H2]ethanol. The rate of acetaldehyde reduction, the degree of labelling of bound NADH and the isotope effect on ethanol oxidation were calculated by fitting models to the found concentrations of ethanols labelled with 1-42H atoms. Control experiments with only [2,2,2-2H3]ethanol showed that there was no loss of the C-2 hydrogens by exchange. The isotope effect on ethanol oxidation appeared to be about 3. Experiments with (1S)-[1-2H]- and [2,2,2-2H3]ethanol indicated that the isotope effect on acetaldehyde oxidation was much smaller. The results indicated that both the rate of reduction of acetaldehyde and the rate of association of NADH with alcohol dehydrogenase were nearly as high as or higher than the net ethanol oxidation. Thus, the rate of ethanol oxidation in vivo is determined by the rates of acetaldehyde oxidation, the rate of dissociation of NADH from alcohol dehydrogenase, and by the rate of reoxidation of cytosolic NADH. In cyanamide-treated rats, the elimination of ethanol was slow but the rates in the oxidoreduction were high, indicating more complete rate-limitation by the oxidation of acetaldehyde.

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Section: The Methodssupporting

confidence: 72%