Meeting Abstract
74.5 Monday, Jan. 6 09:00 Chronic hypoxic incubation of embryonic chickens (Gallus gallus) alters the cardiovascular response to angiotensin analogues. TATE, KB*; CROSSLEY II, DA; Univ. North Texas kevtate@gmail.com
The renin angiotensin system (RAS) is a conserved cardiovascular regulatory system in vertebrates playing a critical role in cardiovascular homeostasis. Angiotensin II (Ang II) is the primary active peptide of the RAS, which is activated in response to hypovolemic/hypotensive stress. Chronic hypoxic conditions have also been suggested to increase RAS activity and elevating circulating levels of Ang II in fetal sheep. Therefore we examined the effects of hypoxic development on the RAS of embryonic chickens (Gallus gallus). We hypothesized that chicken embryos chronically incubated in 15% oxygen would have an attenuated pressor response to angiotensin analogues due to increased circulating levels of Ang II. To test this hypothesis we incubated eggs in 15% oxygen from day 0 up to day 19 (21 day incubation). Hypoxic incubation resulted in embryos that were relatively hypotensive and bradycardic compared to control embryos. Heart rate and blood pressure responses to angiotensin analogues: Angiotensin I, Ang II, and angiotensin converting enzyme (ACE) inhibitor, captopril were assessed. Angiotensin analogues, Ang I and Ang II resulted in a significant increase in arterial pressure in both groups. Hypoxic incubation blunted the response to Ang I suggesting an impact of reduced oxygen on ACE function. Delivery of Ang II prior to ACE inhibition with captopril resulted in a relatively reduced hypertensive response in hypoxic embryos, which was absent following ACE inhibition. These data suggest that Ang II levels are increased by chronic hypoxic incubation, and the conversion of exogenous Ang I to Ang II, is depressed by possibly reduced activity or availability of ACE. Our findings support our hypothesis that cardiovascular responses to exogenous angiotensin analogues are attenuated following chronic hypoxia in embryonic chickens.
