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Measurement of (C 13 )arginine incorporation into apolipoprotein B‐100 in very low density lipoproteins and low density lipoproteins in normal subjects using ( 13 C)sodium bicarbonate infusion and isotope ratio mass spectrometry
Author(s) -
Bennett Michael J.,
Cryer Dennis R.,
Yudkoff Marc,
Coates Paul M.,
Cortner Jean A.,
Marsh Julian B.
Publication year - 1990
Publication title -
biomedical and environmental mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0887-6134
DOI - 10.1002/bms.1200190803
Subject(s) - bicarbonate , chemistry , arginine , sodium bicarbonate , apolipoprotein b , sodium , mass spectrometry , medicine , chromatography , endocrinology , biochemistry , amino acid , cholesterol , organic chemistry
We describe a new stable isotope technique for the in vivo study of hepatic plasma protein synthesis in humans. The method involves the infusion of ( 13 C)sodium bicarbonate for 1 h and the measurement of the isotopic enrichment of ( 13 C)arginine in newly synthesized apolipoprotein B of very low density lipoproteins (VLDL‐apoB) and low density lipoproteins (LDL‐apoB) in blood samples taken over a 5–6 h period from the commencement of the infusion. Isotope ratio mass spectrometry was utilized to measure 13 CO 2 enrichment following hydrolysis of these proteins and conversion of the guanidinium carbon of arginine in the hydrolysate to carbon dioxide by sequential incubation with arginase and urease. The method is capable of measuring isotopic enrichment as low as 0.001 at. % excess (APE) with a precision of 1.2%. In both subjects studied, the ( 13 C)arginine of VLDL‐apoB reached enrichments of 0.2 APE and that of the arginine of LDL‐apoB, 0.03 APE. Incorporation of labeled arginine into LDL‐apoB was demonstrable at 60–90 min. The new technique is safe and is applicable to the study of the hepatic biosynthesis of a wide range of plasma proteins.