Sex differences in blood pressure regulation during ischemic isometric exercise: the role of the β-adrenergic receptors

We sought to investigate whether the beta-adrenergic receptors play a pivotal role in sex-related differences in arterial blood pressure (BP) regulation during isometric exercise. Sixteen volunteers (8 women) performed 2 min of ischemic isometric handgrip exercise (IHE) and 2 min of postexercise circulatory occlusion (PECO). Heart rate (HR) and beat-to-beat arterial BP were continuously measured. Beat-to-beat estimates of stroke volume (ModelFlow) were obtained and matched with HR to calculate cardiac output (Q) over dot and total peripheral resistance (TPR). Two trials were randomly conducted between placebo and nonselective beta-adrenergic blockade (40 mg propranolol). Under the placebo condition, the magnitude of the BP response in IHE was lower in women compared with men. During PECO, the BP remained elevated and the sex differences persisted. The beta-blockade attenuated the BP response during IHE in men (Delta 57 +/- 4 vs. Delta 45 +/- 7 mmHg, P = 0.025) due to a reduction in (Q) over dot (Delta 3.7 +/- 0.5 vs. Delta 1.8 +/- 0.2 L/min, P = 0.012) while TPR was not affected. In women, however, the BP response during IHE was unchanged (Delta 27 +/- 3 vs. Delta 28 +/- 3 mmHg, P = 0.889), despite attenuated (Q) over dot (Delta 2.7 +/- 0.4 vs. Delta 1.3 +/- 0.2 L/min, P = 0.012). These responses were mediated by a robust increase in TPR under beta-blockade (Delta-0.2 +/- 0.4 vs. Delta 2.2 +/- 0.7 mmHg.L-1.min, P = 0.012). These findings demonstrate that the sex differences in arterial BP regulation during ischemic IHE are mediated by beta-adrenergic receptors. NEW & NOTEWORTHY We found that the blood pressure response during isometric exercise in women is mediated by increases in cardiac output, whereas in men it is mediated by increases in both cardiac output and total peripheral resistance. In addition, women showed a robust increase in total peripheral resistance under beta-blockade during isometric exercise and muscle metaboreflex activation. These findings demonstrate that sex differences in blood pressure regulation during isometric exercise are mediated by beta-adrenergic receptors.