title: Exercise-induced changes in plasma vitamin B-6 concentrations do not vary with exercise intensity.
abstract: This study examined the effect of high vs moderate exercise intensity on changes in concentration of plasma pyridoxal 5'-phosphate (PLP), pyridoxal (PL), and 4-pyridoxic acid (4-PA) in human subjects. Eight physically active subjects were tested twice at 60% and 85% maximum oxygen consumption (VO2max) for 30 and 20 min, respectively, on a bicycle ergometer. Blood samples were obtained before and during exercise. Data were adjusted for changes in plasma volume calculated from changes in hematocrit. PLP concentrations significantly increased during exercise (P < 0.0001), with 79% of the rise in PLP concentration occurring within 5 min. 4-PA concentration increased steadily through exercise and was 23% higher at 20 min than at 0 min. Exercise intensity had no effect on the magnitude or rate of either increase for either PLP or 4-PA. PL concentration did not vary with exercise duration, but was significantly higher at 60% compared with 85% VO2max (P = 0.001). No significant differences were observed in glucose concentration. The data do not support hypotheses in the literature that PLP concentration rises during exercise to support exercise-induced shifts in substrate utilization.
authors.affiliation: Department of Exercise and Sports Science, Colorado State University, Fort Collins 80523.
authors.forename: P G
authors.initials: PG
authors.lastname: Crozier
authors.forename: L
authors.initials: L
authors.lastname: Cordain
authors.forename: D A
authors.initials: DA
authors.lastname: Sampson
mesh_terms: D000293:Adolescent; D000328:Adult; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D010101:Oxygen Consumption; D010953:Plasma Volume; D011730:Pyridoxal / Q000097:blood; D011732:Pyridoxal Phosphate / Q000097:blood; D011735:Pyridoxic Acid / Q000097:blood; D011736:Pyridoxine / Q000097:blood*; D013997:Time Factors
chemical_list: D011730:Pyridoxal; D011735:Pyridoxic Acid; D011732:Pyridoxal Phosphate; D011736:Pyridoxine