Mechanisms Causing Myogenic and Reactive Dilation in Rat Soleus Feed Arteries
Authors:Joseph Chin, Douglas Land
Mentor:Jeffrey Jasperse, Professor of Sports Medicine, Pepperdine University
During exercise, active muscles require high levels of blood flow to sustain high levels of activity. This increase in blood flow is controlled primarily by the diameter of feeding arteries and arterioles. The mechanism that induces this dilation is unknown. In previous experiments, this lab has found that arteries actively dilate in response to deformation induced by a brief reduction in intraluminal pressure (magnitude of the dilation dependent on duration of pressure reduction). We investigated if dilation can be induced by other means of deformation that occur under physiologically relevant conditions and the signaling mechanism behind the dilation. Rat soleus feed arteries were isolated and cannulated for in vitro videomicroscopic observation. Deformation protocols with pressure increases from a baseline of 80 cmH2O to 135 cmH2O for 2 sec, 10 sec, 30 sec, 1 min, and 2 min periods followed by a return to baseline pressure all failed to induce dilation (N=7). Reductions in pressure from a baseline of 115 cmH2O to 14 cmH2O for 2 min periods followed by a return to baseline pressure and deformation due to a maintained increase in pressure from 80 cmH2O to 135 cmH2O were conducted in the presence of blockers. 0.5 mM RGD peptide (general vascular integrin blocker) inhibited dilation to a 2 min pressure reduction (max: 31.7±6.8%, inhibited: 10.2±7.5%) but not to a maintained increase in pressure. Washing out the RGD peptide restored dilation. 0.5 mM F11 function blocking antibody (N=6) (β3 integrin blocker) and 0.5 mM amiloride (N=8) (stretch activated channel blocker) failed to inhibit dilation. These data suggest that dilation in response to deformation is dependent on integrins, but not on β3 integrins or stretch activated channels. Dilation due to a temporary pressure reduction and dilation in response to a maintained increase in pressure utilize different mechanisms.