Acetylcholine and insulin‐mediated vasodilation in feed arteries and arterioles of rat skeletal muscle of different fiber type composition

Abstract

Obese, insulin resistant Otsuka Long Evans Tokushima Fatty rats (age 20 wk) were randomly assigned to sedentary (SED), endurance exercise training (EET), interval exercise training (IET), metformin, EET+MET, or IET+MET; and age‐matched Long‐ Evans Tokushima Otsuka rats were assigned to SED or MET. At sacrifice (age 30–32 wk), feed arteries from slow‐twitch soleus (SFA) and fast‐twitch gastrocnemius (GFA) muscles, and second order arterioles from red (G2aR) and white (G2aW) portions of the gastrocnemius muscle were isolated for in vitro assessment of vasomotor responses to acetylcholine (ACh, 10‐9‐10‐4 M), insulin (1–1000 μIU/mL), and sodium nitroprusside (SNP, 10‐9‐10‐4 M). Collapsing across all groups (total n=21), ACh and insulin‐mediated vasodilation in the SFA and G2aR were greater compared to the GFA and G2aW, respectively (all p<0.05). Conversely, SNP‐mediated vasodilation in the GFA was greater compared to the SFA (p<0.05), while G2aR and G2aW exhibited similar responses. Using a heterogeneous group of animals, these data suggest that ACh and insulin‐induced vasodilation is greater in skeletal muscle feed arteries and arterioles perfusing slow‐twitch oxidative muscle fibers than in feed arteries and arterioles perfusing fast‐twitch low oxidative muscle fibers. Support: NIH RO1HL036088, VA CDA‐2 IK2BX001299‐01, AHA 11POST5080002