Mechanisms Underlying Exaggerated Metaboreflex Activation in Prehypertensive Men

Area of Science:

• Physiology
• Cardiovascular Research
• Exercise Science

Background:

• The pressor response to muscle metaboreflex activation is heightened in prehypertension, linked to peripheral vasoconstriction.
• Mechanisms driving this exaggerated response in prehypertension remain unclear.

Purpose of the Study:

• To test the hypothesis that augmented muscle metaboreflex activation in prehypertension results from increased production of muscle metabolites.
• Investigate the role of lactate, potassium (K), and hydrogen ions (H) in this enhanced response.

Main Methods:

• Compared hemodynamic responses (cardiac output, mean arterial pressure, total peripheral resistance) during static exercise and postexercise muscular ischemia in normotensive and prehypertensive men.
• Measured venous blood metabolites and hormones (catecholamines, vasopressin, plasma renin activity) during exercise and ischemia.

Main Results:

• Prehypertensive individuals exhibited significantly higher mean arterial pressure responses to both static exercise and postexercise muscular ischemia.
• Both groups showed increased lactate and decreased pH during postexercise muscular ischemia, with greater changes observed in the prehypertensive group.
• Hormonal responses (vasopressin, renin-angiotensin system) were not elevated in either group during postexercise muscular ischemia.

Conclusions:

• The augmented pressor response to the muscle metaboreflex in prehypertension is associated with greater production of muscle metabolites activating its afferent pathway.
• This enhanced response is not driven by the vasopressin and renin-angiotensin systems or apparent sympathetic nervous system overactivation.
• Arterial stiffness and other prehypertension-specific factors may contribute to the exaggerated pressor response.