Key result
Regional blockade of acid-sensing ion channels with amiloride attenuated increases in mean arterial pressure (+25 vs +30 mmHg, P=0.001) during static handgrip exercise in men.
Why the study?
Although acid-sensing ion channels mediate the skeletal muscle metaboreflex during exercise in animals, whether they play a similar role in humans was unknown.
Does local venous infusion of amiloride attenuate pressor and sympathetic responses to skeletal muscle metaboreflex activation in men?
Does local venous infusion of amiloride attenuate pressor and sympathetic responses to skeletal muscle metaboreflex activation in men?
Absolute Event Rate: 25% vs 30%
p-value: p=0.001
Regional blockade of acid-sensing ion channels with amiloride attenuates increases in arterial pressure and muscle sympathetic nerve activity during static handgrip exercise and postexercise muscle ischemia in humans.
Supports ASIC role in animal metaboreflex; hypothesis-generating for human exercise pressor reflex and requires clinical validation.
In animals, the blockade of acid-sensing ion channels (ASICs), cation pore-forming membrane proteins located in the free nerve endings of group IV afferent fibers, attenuates increases in arterial pressure (AP) and sympathetic nerve activity (SNA) during muscle contraction. Therefore, ASICs play a role in mediating the metabolic component (skeletal muscle metaboreflex) of the exercise pressor reflex in animal models. Here we tested the hypothesis that ASICs also play a role in evoking the skeletal muscle metaboreflex in humans, quantifying beat-by-beat mean AP (MAP; finger photoplethysmography) and muscle SNA (MSNA; microneurography) in 11 men at rest and during static handgrip exercise (SHG; 35% of the maximal voluntary contraction) and postexercise muscle ischemia (PEMI) before (B) and after (A) local venous infusion of either saline or amiloride (AM), an ASIC antagonist, via the Bier block technique. MAP (BAM +30 ± 6 vs. AAM +25 ± 7 mmHg, P = 0.001) and MSNA (BAM +14 ± 9 vs. AAM +10 ± 6 bursts/min, P = 0.004) responses to SHG were attenuated under ASIC blockade. Amiloride also attenuated the PEMI-induced increases in MAP (BAM +25 ± 6 vs. AAM +16 ± 6 mmHg, P = 0.0001) and MSNA (BAM +16 ± 9 vs. AAM +8 ± 8 bursts/min, P = 0.0001). MAP and MSNA responses to SHG and PEMI were similar before and after saline infusion. We conclude that ASICs play a role in evoking pressor and sympathetic responses to SHG and the isolated activation of the skeletal muscle metaboreflex in humans. NEW & NOTEWORTHY We showed that regional blockade of the acid-sensing ion channels (ASICs), induced by venous infusion of the antagonist amiloride via the Bier block anesthetic technique, attenuated increases in arterial pressure and muscle sympathetic nerve activity during both static handgrip exercise and postexercise muscle ischemia. These findings indicate that ASICs contribute to both pressor and sympathetic responses to the activation of the skeletal muscle metaboreflex in humans.
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Campos et al. (2019) studied this question. Amiloride vs. Baseline (before amiloride) and saline infusion was evaluated on Mean arterial pressure (MAP) response to static handgrip exercise (p=0.001). Regional blockade of acid-sensing ion channels with amiloride attenuated increases in mean arterial pressure (+25 vs +30 mmHg, P=0.001) during static handgrip exercise in men.
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