Key result
Bicycle exercise significantly increased plasma norepinephrine (645 to 1151 pg/ml, P<0.001), whereas mental arithmetic and static handgrip did not, failing to consistently reflect sympathetic activity.
Why the study?
Does venous plasma norepinephrine consistently reflect sympathetic nervous activity during different types of stress in patients with untreated essential hypertension?
Observational (n=51)
Does venous plasma norepinephrine consistently reflect sympathetic nervous activity during different types of stress in patients with untreated essential hypertension?
Venous plasma norepinephrine does not consistently reflect sympathetic nervous system activation across all types of physiological and mental stress in hypertensive patients.
Venous norepinephrine may not reliably mark sympathetic activation across stressors; leaves open its validity as a consistent biomarker in hypertension.
To determine whether venous plasma norepinephrine concentrations consistently reflect changes in sympathetic nervous activity, the influence of mental arithmetic, static handgrip, and submaximal bicycle exercise on intra-arterial blood pressure, heart rate, and plasma norepinephrine was studied in 51 subjects with untreated essential hypertension (mean age, 46 years; range, 16-69 years). At rest, plasma norepinephrine was unrelated to age or blood pressure. Mental arithmetic increased mean arterial pressure from 108 +/- 18 to 127 +/- 18 mm Hg (mean +/- S.D.; p less than 0.001) and heart rate from 69 +/- 7 to 93 +/- 13 beats/min (p less than 0.001) but not plasma norepinephrine (547 +/- 297 to 518 +/- 250 pg/ml). Isometric exercise raised mean arterial pressure from 115 +/- 18 to 148 +/- 21 mm Hg (p less than 0.001) and heart rate from 76 +/- 9 to 95 +/- 13 beats/min (p less than 0.001) but not plasma norepinephrine (683 +/- 253 to 741 +/- 253 pg/ml). Bicycle exercise increased mean arterial pressure from 114 +/- 20 to 146 +/- 26 mm Hg (p less than 0.001), heart rate from 77 +/- 9 to 128 +/- 19 beats/min (p less than 0.001), and plasma norepinephrine from 645 +/- 228 to 1151 +/- 462 pg/ml (p less than 0.001). Both the maximum mean arterial pressure and the peak heart rate attained during bicycle exercise were related to the exercise plasma norepinephrine level (r = 0.33, p less than 0.02 and r = 0.28, p less than 0.03, respectively). Increases in plasma norepinephrine with exercise were not greater in older or more hypertensive subjects.(ABSTRACT TRUNCATED AT 250 WORDS)
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Floras et al. (1986) conducted an observational in Untreated essential hypertension (n=51). Physiological stressors (mental arithmetic, static handgrip, bicycle exercise) vs. Rest was evaluated on Plasma norepinephrine concentration during bicycle exercise (pg/ml) (p=<0.001). Bicycle exercise significantly increased plasma norepinephrine (645 to 1151 pg/ml, P<0.001), whereas mental arithmetic and static handgrip did not, failing to consistently reflect sympathetic activity.
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