The arterioles of the cat sartorius muscle dilate when arterial pressure is reduced. It has been suggested that this dilation is due to a decrease in blood flow which in turn decreases oxygen delivery and increases tissue production of vasodilator substances. The latter diffuse into the vicinity of the arterioles and cause vascular relaxation. This vascular dilation acts to maintain blood flow through the tissue near the control level at a time when perfusion pressure is reduced. This phenomenon, called autoregulation of blood flow, has been observed in most organs of the body. In the following experiments, we attempted to test the hypothesis that a fall in the oxygen level of the tissue is responsible for blood flow autoregulation. We did this by studying the response of cat sartorius arterioles to arterial pressure reduction under conditions where the muscle was supplied with oxygen from the environment in addition to that normally supplied by the blood. Tissue PO₂ was altered by placing the isolated, auto-perfused cat sartorius muscle in contact with silicone fluid equilibrated with a 0% to 20% oxygen gas mixture. As oxygen tension in the bathing fluid was increased, the preponderant response was a decrease in arteriolar diameter, blood velocity and arteriolar volume flow. To illustrate, 8% of the arterioles constricted by an average of 10% and 18% when the muscle was exposed to oxygen tensions of 66 and 132 mmHg, respectively. When blood flow autoregulation was investigated, it was found that elevated oxygen tension in the bathing fluid abolished any significant arteriolar dilation or flow autoregulation in the majority of arterioles studied. In addition, the elevated oxygen environment caused complete cessation of blood flow in many of the smaller arterioles (< 15μ in diameter). The results of this study strongly suggest that the O₂ level of the tissue is an important determinant in local blood flow regulation.
| Identifer | oai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/281949 |
| Date | January 1980 |
| Creators | Sullivan, Sharon Marie |
| Contributors | Johnson, Paul C. |
| Publisher | The University of Arizona. |
| Source Sets | University of Arizona |
| Language | en_US |
| Detected Language | English |
| Type | text, Dissertation-Reproduction (electronic) |
| Rights | Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. |
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