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Gas chromatographic/mass spectrometric analysis of stable isotopes of 3‐methylhistidine in biological fluids: Application to plasma kinetics in vivo
Author(s) -
Rathmacher J. A.,
Link G. A.,
Flakoll P. J.,
Nissen S. L.
Publication year - 1992
Publication title -
biological mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1052-9306
DOI - 10.1002/bms.1200211107
Subject(s) - chemistry , chromatography , urine , elution , gas chromatography , isotope , biochemistry , physics , quantum mechanics
A simple and rapid method for measuring 3‐methylhistidine (3MH) in plasma and urine is described. Internal standard, 1‐methylhistidine (1MH), was added to plasma, acidified and absorbed onto cation‐exchange columns. It was then eluted from columns, dried, and derivatized for gas chromatography/mass spectrometry. A major fragment of 3MH was monitored at 238 u and 3‐methyl‐(methyl‐ 2 H 3 )histidine ( d 3 ‐3MH) (used for in vivo kinetics) at 241 u, whereas 1MH was monitored at 340 u and eluted 0.5 min later than 3MH. Standard curves for plasma analysis were linear and nanamole amounts of 3MH in plasma were determined with a precision of 3.5%. 3MH was also quantitated in urine; however, because of substantial amounts of 1MH, ( 18 O 2 )1MH was used as the internal standard. Nanamole amounts of 3MH were determined in urine with a precision of 2.7%. Application of the 3MH analytical method was used to develop a kinetic compartmental model by using the stable isotope of 3MH, d3 ‐3MH. Cattle, like humans, quantitatively excrete 3MH in the urine. A young bovine was injected with d3 ‐3MH and the enrichment curve in plasma was evaluated in order to obtain a steady‐state production rate of 3MH. The decay curve was modeled through the use of NIH‐SAAM modeling program. The kinetics of d3 ‐3MH from plasma were adequately described by a three‐pool compartmental model. The de novo production rate of 3MH estimated in the calf was 665 μmol per day. This corresponded to an estimated fractional turnover rate of 1.56% per day, which was similar to estimates obtained from urine collections. These data suggest that d3 ‐3MH can be used to model 3MH production in vivo .