Journal of Applied Physiology AJP: Endocrinology and Metabolism
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J Appl Physiol 87: 2259-2265, 1999;
8750-7587/99 $5.00
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Vol. 87, Issue 6, 2259-2265, December 1999

Arteriolar reactivity and capillarization in chronically stimulated rat limb skeletal muscle post-MI

D. Paul Thomas1 and Olga Hudlická2

1 School of Physical and Health Education, University of Wyoming, Laramie, Wyoming 82071; and 2 Department of Physiology, University of Birmingham Medical School, Birmingham B15 2TT, United Kingdom

The purpose of this study was to assess whether electrical stimulation-induced increases in muscular activity could improve capillary supply and correct previously documented abnormal vasodilator and vasoconstrictor responses of arterioles in limb skeletal muscle post-myocardial infarction (MI). Extensor digitorum longus (EDL) muscle from rats with surgically induced MI (~30% of the left ventricle) was chronically stimulated (Stim) 8 h/day for 6 ± 1 days, at 11 wk post-MI. Third- (3A) and fourth-order (4A) arterioles in EDL from nine MI rats and four MI+Stim rats were compared with those of 11 controls (Con). Compared with Con rats, MI alone caused a reduction in the resting diameter of 3A and 4A arterioles, which was completely reversed by MI+Stim. However, Stim did not correct the attenuated vasodilator response to 10-4 M adenosine seen in 4A arterioles from MI rats compared with Con. The constrictor response of both 3A and 4A vessels in MI rats to low doses of acetylcholine (10-9 M, 10-8 M) and norepinephrine (10-9 M) was accentuated in MI+Stim. The proportion of oxidative fibers in EDL was unaffected by MI or MI+Stim combination. However, Stim significantly increased (P < 0.05) the capillary-to-fiber ratio in this muscle compared with Con. Thus, although the increase in muscle activity induced by chronic electrical stimulation normalized the reduction in resting vessel diameter seen after MI, it failed to correct the abnormalities in vasoreactivity of these same vessels.

endothelium; skeletal muscle activity; nitric oxide; heart failure





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