Aharinejad S, Böck P
Institute of Anatomy I, University of Vienna, Austria.
Scanning Microsc. 1992 Sep;6(3):865-73; discussion 873-5.
The appearance of pulmonary venous sphincters was studied in normotensive and spontaneously hypertensive rats using scanning electron microscopy of microvascular corrosion casts and transmission electron microscopy of tissue sections. Vascular casts were prepared either after lavage with Tyrode solution or after glutaraldehyde prefixation. Pronounced pulmonary venous sphincters were more frequently identified in spontaneously hypertensive rats as compared to corresponding circular indentations in normotensive rats. Tissue sections established venous sphincters in hypertensive animals as consisting of multiple layers of smooth muscle cells in the venous walls. We did not observe any autonomic nerve terminals in close proximity to these bundles of smooth muscle cells. The effect of various casting procedures on the appearance of venous sphincters is discussed. It is concluded that glutaraldehyde prefixation is an appropriate method to demonstrate sphincter functioning, because it causes deepening of sphincter indentations. Pulmonary vascular sphincters are thought to be governed by blood-born substances, vasoactive metabolites, or by tension of oxygen and carbon dioxide. Venous sphincters may influence microvascular flow in general and probably substitute for venous valves in the pulmonary vascular bed where valves are missing.
利用微血管铸型扫描电子显微镜和组织切片透射电子显微镜，对正常血压大鼠和自发性高血压大鼠的肺静脉括约肌外观进行了研究。血管铸型是在经台氏液灌洗后或戊二醛预固定后制备的。与正常血压大鼠相应的圆形压痕相比，自发性高血压大鼠中更频繁地发现明显的肺静脉括约肌。组织切片证实高血压动物的静脉括约肌由静脉壁中的多层平滑肌细胞组成。我们在这些平滑肌细胞束附近未观察到任何自主神经末梢。讨论了各种铸型制备程序对静脉括约肌外观的影响。得出的结论是，戊二醛预固定是展示括约肌功能的一种合适方法，因为它会导致括约肌压痕加深。肺血管括约肌被认为受血液中的物质、血管活性代谢产物或氧气和二氧化碳张力的调节。静脉括约肌可能总体上影响微血管血流，并且可能在缺乏瓣膜的肺血管床中替代静脉瓣膜。
