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[RC] Endurance exercise/blood flow - Ridecamp Guest

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Authors RM McAllister, JL Jasperse, MH Laughlin
Title   Nonuniform effects of endurance exercise training on vasodilation in 
rat skeletal muscle
Full source     Journal of Applied Physiology, 2005, Vol 98, Iss 2, pp 753-761

Endurance exercise training ( Ex) has been shown to increase maximal skeletal 
muscle blood flow. The purpose of this study was to test the hypothesis that 
increased endothelium-dependent vasodilation is associated with the Ex-induced 
increase in muscle blood flow. Furthermore, we hypothesized that enhanced 
endothelium-dependent dilation is confined to vessels in high-oxidative muscles 
that are recruited during Ex. To test these hypotheses, sedentary ( Sed) and 
rats that underwent Ex (30 m/min x 10% grade, 60 min/day, 5 days/wk, 8-12 wk) 
were studied using three experimental approaches. Training effectiveness was 
evidenced by increased citrate synthase activity in soleus and vastus lateralis 
(red section) muscles (P < 0.05). Vasodilatory responses to the 
endothelium-dependent agent acetylcholine (ACh) in situ tended to be augmented 
by training in the red section of gastrocnemius muscle (RG; Sed: control, 0.69 
&PLUSMN; 0.12; ACh, 1.25 &PLUSMN; 0.15; Ex: control, 0.86 &PLUSMN; 0.17; ACh, 
1.76 &PLUSMN; 0.27 ml.min(-1).100 g(-1).mmHg(-1); 0.05 < P < 0.10 for Ex vs. 
Sed during ACh). Responses to ACh in situ did not differ between Sed and Ex for 
either the soleus muscle or white section of gastrocnemius muscle (WG). 
Dilatory responses of second-order arterioles from the RG in vitro to flow (4-8 
&mu;l/min) and sodium nitroprusside (SNP; 10(-7) through 10(-4) M), but not 
ACh, were augmented in Ex (vs. Sed; P < 0.05). Dilatory responses to ACh, flow, 
and SNP of arterioles from soleus and WG muscles did not differ between Sed and 
Ex. Content of the endothelial isoform of nitric oxide synthase ( eNOS) was 
increased in second-order, fourth-order, and fifth-order arterioles from the RG 
of Ex; eNOS content was similar between Sed and Ex in vessels from the soleus 
and WG muscles. These findings indicate that Ex induces endothelial adaptations 
in fast-twitch, oxidative, glycolytic skeletal muscle. These adaptations may 
contribute to enhanced skeletal muscle blood flow in endurance-trained 
individuals.


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