FLOW-INDUCED DILATION IN RAT SOLEUS FEED ARTERIES AFTER ALTERED PHYSICAL ACTIVITY 997

Abstract

Flow-induced dilation (FID) in conduit arteries and skeletal muscle arterioles has been reported to be enhanced after exercise training or chronic increases in blood flow. We tested the hypothesis that rat soleus feed arteries (SFA), which contribute a significant proportion of the total vascular resistance to a muscle, would 1) exhibit enhanced FID following exercise training, and 2) exhibit attenuated FID following hindlimb unweighting. SFA from exercise trained (EX; n=7) (treadmill running: 30m/min, 15% incline, 1 hr/d,5d/wk, 10-12 wks), hindlimb unweighted (HLU; n=5)(14 days), and sedentary control (CON; n=10) rats were isolated and cannulated with two glass pipettes connected to independent reservoirs in two different sets of experiments. Intraluminal pressure was maintained at 90 cmH2O throughout the experiment. Flow was induced through SFA by raising one reservoir while lowering the other an equal distance. SFA from all groups dilated markedly to flows of 10-60 ul/min, but dilation of SFA from EX and HLU did not differ from dilation of SFA from CON (maximal dilation: CON: 61±8%, EX: 55±9%, HLU: 56±19%). Thus chronic changes in blood flow induced by EX or HLU did not alter FID in rat SFA. Since SFA blood flow in the resting rat (-90 ul/min) is well above that necessary to produce maximal FID (Physiologist 39:A-45, 1996), changes in flow associated with EX and HLU may not provide an adequate stimulus for alteration of flow signalling mechanisms.