Norepinephrine metabolism in humans studied by deuterium labelling: turnover of 4-hydroxy-3-methoxyphenylglycol.
D,L(+/-)-4-Hydroxy-3-methoxyphenylglycol (HMPG) labelled with three deuterium atoms was used to study turnover of plasma free HMPG following an intravenous injection. Ten healthy men were given a pulse dose of either 4.3 mumol or 2.2 mumol of labelled HMPG ([2H3]HMPG piperazine salt). Plasma and urine levels of both endogenous and labelled HMPG were subsequently followed by gas chromatography-mass spectrometry with selected ion detection. Kinetic calculations based upon a single-compartment model were consistent with a monoexponential elimination of plasma free HMPG. The half-life of HMPG was 0.46 and 0.78 h (mean values in the two dose groups). The HMPG production rate was 2.01 and 2.35 mumol/hour, and the urinary excretion rate of HMPG (free and conjugated) was 0.48 and 0.47 mumol/h. The endogenous plasma level of free HMPG was 25 and 33 nmol/L. The results show that HMPG turns over rapidly and that HMPG is further metabolized extensively. About one-fourth of the HMPG produced is excreted in urine as free and conjugated HMPG.
D000328:Adult; D003903:Deuterium; D006018:Glycols / Q000378:metabolism*; D006801:Humans; D007275:Injections, Intravenous; D007700:Kinetics; D008297:Male; D008734:Methoxyhydroxyphenylglycol / Q000008:administration & dosage / Q000378:metabolism*; D008875:Middle Aged; D009638:Norepinephrine / Q000378:metabolism*
D006018:Glycols; D008734:Methoxyhydroxyphenylglycol; D003903:Deuterium; D009638:Norepinephrine