ISSN:
1471-4159
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
Abstract: A double isotope labelling technique was used to simultaneously determine the in vivo turnover rates of 4-hydroxy-3-methoxyphenylglycol (HMPG) and 4-hydroxy-3-methoxymandelic acid (HMMA, VMA) and the rate of HMPG oxidation to HMMA. Six healthy men were given intravenous injections of [2H3]HMPG and [2H6]HMMA and their plasma and urine samples analysed by gas chromatography-mass spectrometry (GC/MS) for the protium and deuterium species. HMPG and HMMA production rates were calculated by isotope dilution. The rate of HMPG oxidation to HMMA was obtained from the fraction of [2H3]HMPG recovered as [2H3]HMMA. The results showed that the entire production of HMMA, 1.11 ± 0.21 μmol/h (mean ± SE), could be accounted for by oxidation of HMPG, 1.49 ± 0.31 μmol/h. In another experiment designed to avoid expansion of the HMPG body pool, a tracer dose of [14C]HMPG was given to the same subjects. The levels of [14C]HMPG and [14C]HMMA were measured in urine after extraction and separation by thin layer chromatography. Urinary excretion of endogenous HMPG and HMMA was determined by GC/MS. The results showed that the endogenous HMMA fraction of the total HMPG and HMMA urinary excretion rate, 0.57 ± 0. 04, was the same as the fraction of [14C]HMPG oxidized to [14C]HMMA, 0.62 ± 0.01. Thus, HMPG is the main intermediate in the metabolic conversion of norepinephrine and epinephrine to HMMA in man.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1471-4159.1984.tb09695.x
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