Oxygen-mediated regulation of neonatal and adult rabbit aortic tension

To determine the influence of oxygen on aortic tension in young and mature animals, we evaluated the response of neonatal and adult rabbit aortic rings to changes in oxygen tension. In 95% nitrogen/5% carbon dioxide, endothelium-derived nitric oxide was not a factor in the development or maintenance of low resting aortic ring tensions. However, the production of endothelium-derived nitric oxide increased in 21% oxygen/74% nitrogen/5% carbon dioxide and 95% oxygen/5% carbon dioxide, and attenuated a concomitant endothelium-independent mechanism of increasing vascular tension. A protein kinase inhibitor, 0.2 mM 1-(5-isoquinolinyl-sulfonyl)-2-methyl piperazine (H-7) inhibited oxygen-mediated constriction of neonatal vessels, but also significantly reduced the contractile response to 60 mM KCl. In conclusion, resting aortic tension is in part determined by oxygen-mediated control of the production of endothelium-derived nitric oxide and one or more opposing endothelium-independent mechanisms of constriction.