Dickhout J G, Lee R M
Department of Anaesthesia, McMaster University, Hamilton, Ontario, Canada.
Hypertension. 1997 Mar;29(3):781-9. doi: 10.1161/01.hyp.29.3.781.
We studied structural and functional changes of small muscular arteries from the mesenteric vascular bed of young spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY) using a new morphometric protocol involving the use of confocal microscopy and a pressurized artery system. At 3 and 4 weeks of age, systolic pressure of SHR and WKY was similar; however, significant structural changes in the mesenteric vasculature were already present in SHR. Arteries fixed under pressure in vitro from SHR had a larger medial volume and increased number of smooth muscle cell layers but similar lumen size compared with arteries from WKY in maximally relaxed conditions. Functional studies showed that SHR arteries contracted more in response to stimulation by KCl and norepinephrine, resulting in a significantly smaller lumen size in these vessels than in those from WKY. SHR arteries precontracted with KCl were also able to maintain a smaller lumen diameter than WKY arteries when challenged with increasing pressure levels. No difference in the sensitivity of response of these arteries to norepinephrine stimulation was found. At 3 and 4 weeks of age, mesenteric arteries from some SHR and WKY were not responsive to periarterial nerve stimulation, and the number of responders was higher in the WKY than SHR. However, a greater degree of contraction was found in SHR arteries responding to field stimulation at 4 weeks than in WKY arteries. We conclude that there is a temporal difference in the rate of functional maturation of the innervation in SHR arteries compared with WKY arteries. Structural changes of the small muscular arteries, caused by an increase in the medial volume, and increased number of smooth muscle cell layers are primary changes that contribute to the development of hypertension in the SHR because these changes are present at the age when blood pressure is similar in SHR and WKY.
我们使用一种新的形态测量方法，包括共聚焦显微镜和加压动脉系统，研究了年轻的自发性高血压大鼠（SHR）和正常血压的Wistar-Kyoto大鼠（WKY）肠系膜血管床中小肌性动脉的结构和功能变化。在3周和4周龄时，SHR和WKY的收缩压相似；然而，SHR的肠系膜血管已经出现了显著的结构变化。与在最大舒张状态下的WKY动脉相比，体外加压固定的SHR动脉具有更大的中膜体积和平滑肌细胞层数增加，但管腔大小相似。功能研究表明，SHR动脉对氯化钾和去甲肾上腺素刺激的收缩反应更强，导致这些血管的管腔大小明显小于WKY动脉。用氯化钾预收缩的SHR动脉在压力增加时也能够维持比WKY动脉更小的管腔直径。未发现这些动脉对去甲肾上腺素刺激的反应敏感性有差异。在3周和4周龄时，一些SHR和WKY的肠系膜动脉对动脉周围神经刺激无反应，WKY中反应者的数量高于SHR。然而，4周时对场刺激有反应的SHR动脉的收缩程度比WKY动脉更大。我们得出结论，与WKY动脉相比，SHR动脉神经支配功能成熟的速率存在时间差异。小肌性动脉的结构变化，由中膜体积增加和平滑肌细胞层数增加引起，是导致SHR高血压发展的主要变化，因为这些变化在SHR和WKY血压相似的年龄就已存在。
