Potassium Channel Role in EDHF-Induced Dilation of Soleus Feed Arteries from Sedentary and Short-term Exercise Trained Rats

Endothelium-derived hyperpolarizing factors (EDHF) may act through one or more K+ channels. We tested the hypothesis that specific K+ channels (KV, KATP, KIR and Na-K pump) mediate the EDHF response and that short term exercise training (STEX)(4 wks) increases the K+ channel role. STEX rats ran on a treadmill at 30m/min for 1 hr/d, 5 d/wk. Soleus feed arteries (n=37) were isolated, cannulated and pressurized at 90 cm H20. STEX did not alter the effect of K+ channel inhibition on ACh (10−9-10−4M) dilation, so data from SED and STEX rats are combined. In Group 1, ACh caused 87.3 ± 2.8% dilation, which was reduced by KV (1mM 4-aminopyradine) inhibition to 80.1 ± 3.5% dilation, and reduced further by combined Kv and KATP inhibition (50 μM glibenclamide) (41.5 ± 7.5%). In Group 2, ACh caused 80.6 ± 7.2% dilation. NO (300 μM L-NNA )and PGI2 (5 μM indomethacin) inhibition reduced dilation to 31.4 ±9.5%. Adding KV inhibition did not further decrease dilation, but adding combined KV and KATP inhibition reduced dil...