Mechanisms of Reduced Vascular Tone Following Arteriogenesis Induced by Femoral Artery Ligation
College - Author 1
College of Engineering
Department - Author 1
Biomedical Engineering Department
Degree Name - Author 1
BS in Biomedical Engineering
The presence of a developed, native collateral network can decrease the severity of ischemic injury proceeding arterial occlusion. The collateral network must under arteriogenesis to enlarge and increase blood flow to the ischemic region. Although there has been tremendous effort attempting to understand the mechanisms of arteriogenesis, no therapies have been successful in improving patient outcome. To better understand the mechanisms involved in arteriogenesis, the effect of nitric oxide production, myogenic tone, and a-adrenergic receptors were evaluated as these have been identified as playing an important role in vascular injury. Arteriogenesis was induced by ligating the femoral artery between the epigastric and popliteal branches in male C57/BL6 mice between two to four months old. Pharmacological agents were dissolved in a physiological salt solution that was superfused over the exposed gracilis anterior to generate does response curves. The collateral diameter was measured using intravital microscopy. Diameter measurements were normalized to resting diameter to create percent changes for the operated vessels and contralateral sham. Procedures were performed at both seven and twenty-eight days following femoral artery ligation to evaluate how pathways changed with the restoration of vascular tone. Nitric oxide production does not appear to play an important role as the values for the day seven (-47 ± 7% for the operated and -43 ± 5% for the contralateral control) were similar to day twenty-eight (-31 ± 5% vs -27 ± 4 %, control and operated respectively). Myogenic tone does not appear to play an important role as the values for day seven (19 ± 3% for ligated and 31 ± 7% for the sham) are similar to day twenty-eight (25 ± 3% vs 39 ± 6%, ligated and sham respectively). a-adrenergic receptor stimulation appears to play an important role as there is a heightened response at day seven (-71 ±7 % vs -39 ± 6%, ligated vs sham respectively) compared to day twenty-eight ( -44 ± 4 % vs -31 ± 9%, ligated vs sham respectively). However, inhibition did not appear to be significant because there is a lack of response at both day seven (16 ± 9% vs 73 ±15 %, ligated vs sham, respectively) and day twenty-eight (16 ± 7% vs 50 ±7%, ligated vs sham, respectively). These findings suggest that there is lack of sympathetic innervation seven days after ligation that is restored twenty-eight days later.