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Influence of p2-Adrenergic Receptor Genotype on Airway Function During Exercise in Healthy Adults: Catecholamine Response to Exercise

Published in Pulmonary Function

Figure 1 shows the changes in arterial levels of epinephrine and norepinephrine during low- and high-intensity exercise as well as during recovery (expressed as the percentage change from rest). No significant differences were observed between groups, although the Arg16 subjects tended to have a greater increase in epinephrine than the Gly16 subjects (p = 0.07).
Small changes were observed in FEF50 with low-intensity exercise in each genotype group (3 to 6%; p = 0.002 from rest). Both groups demonstrated similar increases in bronchodilation during heavy exercise (averaging 14% and 15% for the homozygous Arg16 and Gly16 subjects, respectively, over the last 3 min of exercise; p < 0.001, from rest), and there were no statistically significant differences between the Arg16 and Gly16 groups in the degree of bronchodilation (Fig 2). During the recovery period, at 5 min and 10 min after exercise, both groups had a decrease in FEF50, but the FEF50 returned to baseline or below in 12 of 16 Arg16 subjects, while 20 of 26 Gly16 subjects had sustained, mild bronchodilation (p < 0.001).

The FEF25-75 showed similar changes during and after exercise, with the Arg16 subjects falling to near baseline values (— 0.72 ± 2.8%), while the Gly16 subjects had a sustained increase (+ 8.0 ± 2.4%) at 10 min after exercise. We performed a post hoc subanalysis of the changes in FEF50 during exercise and recovery based on position 27 of the P2AR (Table 3). All Arg16 subjects were homozygous for glutamine at position 27, creating an Arg16/Gln27 homozygous haplotype. Of the Gly16 homozygotes, 6 homozygotes (23%) were homozygous for glutamine (Gly16/ Gln27), 11 homozygotes (42%) were homozygous for glutamate (Gly16/Glu27), and 9 homozygotes (35%) were heterozygous (Gly16Gly/Gln27Glu). While the group numbers were too small for any meaningful statistical analysis, the homozygous Gly16/Gln27 haplotypes tended to have the largest changes in FEF50 with heavy exercise, followed by the Gly16Gly/Gln27Glu group, then the Arg16/Gln27 haplotype, and finally the Gly16/Glu27 haplotype. None of the differences that were observed at 5 min and 10 min of recovery could be explained by position 27. birthcontroltab.com

Figure-1

Figure 1. Epinephrine (Epi) and norepinephrine (NorEpi) response to exercise. The dashed Lines represent the Arg16 group, while the solid lines represent the Gly16 group (values are mean ± SE). The lines with the black circular bullets (•) represent epinephrine, while the lines with the gray square bullets (■) represent norepinephrine. Both groups had little change in epinephrine and norepinephrine at the lower workload. In contrast, both groups had marked increases in epinephrine and norepinephrine at the higher workload. Although the Arg16 group had higher epinephrine levels at the higher workload (p = 0.07), there were no significant differences between the groups. Max = maximum.

Figure-2

Figure 2. Percent change in FEF50 during exercise and recovery. The dashed line represents the Arg16 group, while the solid line represents the Gly16 group (values are mean ± SE). Both had small increases in FEF50 at the lower workload (p = 0.002, from rest). At the higher workload, both groups had further increases in FEF50 (p < 0.001, from rest); however there were no significant differences between the groups. During recovery, FEF50 in the Arg16 group quickly returned to baseline, while in the Gly16 group FEF50 tended to remain elevated (p < 5.55l).

Table 3—Percentage Change in FEF50 During Exercise and Recovery According to Positions 16 and 27 of the P2AR

Position 27 Arg16 Gly16
Gln/Gln (n = 16, 100% of Subjects) Gln/Gln (n = 6, 23% of Subjects) Gln/Glu (n = 11,42% of Subjects) Glu/Glu (n = 9,35% of Subjects) p Value, ANOVA (Gly16)
FEF50 (40% of peak) 2+ 13 2±6 2±9 2±4 0.07
FEF50 (75% of peak) 12 ± 3 15 ± 1 14 ± 2 2±8 0.02
FEF50 (5-min recovery) 2±2 2±7 3 ± 1 2±5 0.70
FEF50 (10-min recovery) 3±31 2±8 2±7 2±7 0.96