Nitric oxide (NO) is an important mediator of angiogenesis and is primarily produced endogenously through the action of nitric oxide synthase (NOS). An alternate pathway for NO production is the conversion of nitrite to NO, which depends on the presence of hemoglobin (Hb) and hypoxic conditions. The angiogenic effects of topically applied sodium nitrite on two vascular beds in the ex ovo chicken embryonic model of angiogenesis were assessed. Gas barrier films were used to modulate local oxygen levels in the chorioallantoic membrane (CAM), a respiratory vascular network, and the area vasculosa (AV) on the yolk sac, a typical peripheral vascular network. The low-permeable film polyvinylidene chloride (PVDC) and highly permeable regenerated cellulose (RC) were applied to the surface of the vasculature to alter oxygen diffusion and transport and produce a local environment of low or high oxygen, respectively. Phosphorescence Quenching Microscopy (PQM) was used to verify the oxygen levels in the vascular membranes underneath the films. Following 48 hours of continuous application of sodium nitrite (330 μg/kg/day), saline, or sodium nitrite + cPTIO (a NO scavenger) (1mg/kg/day), the angiogenic response was quantified by measuring vascular density and network complexity. The PVDC film reduced CAM PO2 to 17.9±5.5 mmHg and AV PO2 to 29.5±3.6 while the RC film maintained a PO2 of 115 mmHg. At the edge of PVDC film, there was found to be a small area of transition between the nearby low and high PO2 regions. After nitrite application, significant increases in vascularity were observed in the AV under hypoxic conditions, but not normoxic conditions (p<0.03). cPTIO inhibited nitrite-induced angiogenesis and returned vascularity to levels observed with saline application. No significant changes were observed in the CAM, but a trend of reduced angiogenesis after nitrite application was observed compared to saline and saline+cPTIO. These results indicate that two highly diffusible gases, NO and O2, play important roles in the growth of new blood vessels, but in a way that appears to depend on the gas exchange function of the vascular network.
| Identifer | oai:union.ndltd.org:vcu.edu/oai:scholarscompass.vcu.edu:etd-4210 |
| Date | 01 October 2013 |
| Creators | Connery, Michael |
| Publisher | VCU Scholars Compass |
| Source Sets | Virginia Commonwealth University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations |
| Rights | © The Author |
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