Journal article
α-Adrenergic Blockade Unmasks a Greater Compensatory Vasodilation in Hypoperfused Contracting Muscle
Frontiers in physiology, Vol.3, pp.271-271
2012
DOI: 10.3389/fphys.2012.00271
PMCID: PMC3429045
PMID: 22934025
Abstract
We previously demonstrated that acute hypoperfusion in exercising human muscle causes an immediate increase in vascular resistance that is followed by a partial restoration (less than 100% recovery) of flow. In the current study we examined the contribution of α-adrenergic vasoconstriction in the initial changes in vascular resistance at the onset of hypoperfusion as well as in the recovery of flow over time. Nine healthy male subjects (29 ± 2) performed rhythmic forearm exercise (20% of maximum) during hypoperfusion evoked by intra-arterial balloon inflation. Each trial included; baseline, exercise prior to inflation, exercise with inflation, and exercise after deflation (3 min each). Forearm blood flow (FBF; ultrasound), local (brachial artery), and systemic arterial pressure (MAP; Finometer) were measured. The trial was repeated during phentolamine infusion (α-adrenergic receptor blockade). Forearm vascular conductance (FVC; ml min
−1
100 mmHg
−1
) and resistance (mmHg ml min
−1
) was calculated from BF (ml min
−1
) and local MAP (mmHg). Recovery of FBF and FVC (steady state inflation plus exercise value − nadir)/[steady state exercise (control) value − nadir] with phentolamine was enhanced compared with the respective control (no drug) trial (FBF = 97 ± 5% vs. 81 ± 6%,
P
< 0.05; FVC = 126 ± 9% vs. 91 ± 5%,
P
< 0.01). However, the absolute (0.05 ± 0.01 vs. 0.06 ± 0.01 mmHg ml min
−1
;
P
= 0.17) and relative (35 ± 5% vs. 31 ± 2%;
P
= 0.41) increase in vascular resistance at the onset of balloon inflation was not different between the α-adrenergic receptor inhibition and control (no drug) trials. Therefore, our data indicate that α-adrenergic mediated vasoconstriction restricts compensatory vasodilation during forearm exercise with hypoperfusion, but is not responsible for the initial increase in vascular resistance at the onset of hypoperfusion.
Details
- Title: Subtitle
- α-Adrenergic Blockade Unmasks a Greater Compensatory Vasodilation in Hypoperfused Contracting Muscle
- Creators
- Darren P Casey - Human and Integrative Physiology Laboratory, Department of Anesthesiology, Mayo ClinicMichael J Joyner - Human and Integrative Physiology Laboratory, Department of Anesthesiology, Mayo Clinic
- Resource Type
- Journal article
- Publication Details
- Frontiers in physiology, Vol.3, pp.271-271
- DOI
- 10.3389/fphys.2012.00271
- PMID
- 22934025
- PMCID
- PMC3429045
- NLM abbreviation
- Front Physiol
- ISSN
- 1664-042X
- eISSN
- 1664-042X
- Publisher
- Frontiers Research Foundation
- Language
- English
- Date published
- 2012
- Academic Unit
- Physical Therapy and Rehabilitation Science; Fraternal Order of Eagles Diabetes Research Center
- Record Identifier
- 9984047648902771
Metrics
25 Record Views