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DISTRIBUTION AND TURNOVER RATE OF VANILLYL‐MANDELIC ACID AND 3‐METHOXY‐ 4‐ HYDROXYPHENYLGLYCOL IN RAT BRAIN
Author(s) -
Karoum F.,
Neff N. H.,
Wyatt R. J.
Publication year - 1976
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1976.tb01539.x
Subject(s) - probenecid , pargyline , chemistry , homovanillic acid , mandelic acid , endocrinology , norepinephrine , medicine , vanillylmandelic acid , chromatography , dopamine , monoamine oxidase , biochemistry , serotonin , organic chemistry , receptor , enzyme
— Vanillylmandelic acid (VMA) and 3‐methoxy‐4‐ hydroxyphenylglycol (MHPG) were measured in rat brain by a mass fragmentographic procedure. The concentration of VMA and MHPG in whole brain is 11 and 533 pmol/g, respectively. Both compounds were found in all areas of brain studied with VMA, as a percentage of both metabolites, ranging between about 1 and 8%. From the decline of the compounds after pargyline. 75 mg/kg i.p., we calculated that the rate of formation of VMA is 15 and for MHPG 202 pmol/g per h. The fractional rate of elimination of VMA and MHPG is 1.4 and 0.38 h −1 , respectively. The rapid rate of loss of VMA suggests that it is transported from brain. However, we were unable to block the elimination of VMA from brain by treatment with probenecid. In contrast, the elimination of MHPG could be blocked by treatment with probenecid. Our study adds support to the notion that MHPG is a major whereas VMA is a minor product of norepinephrine metabolism in brain.