Myophosphorylase Knock Out Prevents the Exaggerated Exercise Pressor Reflex in Rats With Simulated Peripheral Artery...

Area of Science:

• Physiology
• Cardiovascular Research
• Metabolic Regulation

Background:

• Peripheral artery disease (PAD) is associated with an exaggerated exercise pressor reflex (EPR).
• The specific metabolites responsible for this exaggerated EPR in PAD remain debated.
• Understanding these factors is crucial for managing cardiovascular complications in PAD patients.

Purpose of the Study:

• To investigate the role of lactate and hydrogen ions in the exaggerated EPR in a rat model of PAD.
• To differentiate the contribution of metabolic factors versus mechanical factors to the EPR in PAD.

Main Methods:

• A rat model of PAD was created by ligating the femoral artery for 72 hours.
• Muscle-specific knockout of myophosphorylase (pygm) was used to manipulate lactate and hydrogen ion production.
• The exercise pressor reflex was evoked by static muscle contraction, and responses were compared between ischemic and non-ischemic limbs.

Main Results:

• In wild-type rats with PAD, static contraction, lactic acid, and phosphate injections showed significantly greater pressor responses compared to controls.
• In pygm knockout rats, femoral artery ligation did not affect the pressor response, indicating lactate and hydrogen ions are critical.
• Femoral artery ligation exacerbated the pressor response to passive stretch in both groups.

Conclusions:

• Accumulation of lactate and hydrogen ions in contracting myocytes is a key factor in exaggerating the metabolic component of the EPR in PAD.
• These metabolites play a critical role in the heightened cardiovascular response observed during exercise in PAD.
• Targeting these metabolic pathways could offer therapeutic strategies for managing PAD-related cardiovascular dysfunction.