自发性高血压大鼠肠系膜小动脉血管肌源性紧张度的时程变化

Time-course changes of myogenic tone of mesenteric small artery in spontaneously hypertensive rat

本文旨在观察自发性高血压大鼠(spontaneously hypertensive rat,SHR)肠系膜小动脉(mesenteric small artery,MSA)血管肌源性紧张度的时程变化。将32只SHR大鼠随机分为8、16、24以及32周龄组,另以正常Wistar-Kyoto(WKY)大鼠为对照组。采用压力型小动脉测量仪在含Ca2+(2.5mmol/L)或无Ca2+生理盐溶液(physiologic salt solution,PSS)中分别测量不同管腔压力下血管的主动态管径(active diameter,Da)和被动态管径(passive diameter,Dp)。肌源性紧张度由(Dp?Da)/Dp×100%表示。分别观察8、16、24以及32周龄大鼠MSA血管肌源性紧张度的时程变化,并进一步观察血管肌源性紧张度与血压之间的关系。结果显示,与对照组相比,SHR大鼠尾动脉压力、血管肌源性紧张度显著增高。SHR大鼠MSA血管肌源性紧张度在24周以前单调增大,但32周SHR大鼠血管肌源性紧张度与24周相比有所降低,但仍显著高于对照组;同时SHR大鼠尾动脉压力随周龄增加而缓慢单调增大,32周大鼠尾动脉压力与24周相比仍显著增加。上述结果提示:血管肌源性紧张度作用参与了高血压病发生发展的整个过程,在高血压发展早期,由于血管紧张度的代偿性作用,血管功能得到一定程度的纠正,保证正常器官供血;在高血压病晚期,由于血管肌源性紧张度作用失代偿,血管功能受到破坏,并由此导致严重的疾病。

To investigate the time-course changes of myogenic tone in mesenteric small artery （MSA） of spontaneously hypertensive rat （SHR）, thirty-two 7-week aged SHR rats were randomly divided into four groups （8, 16, 24, 32 weeks of age）, and 32 sexand agematched Wistar-Kyoto （WKY） rats were assigned to control groups （CON）. On the day of the study, segments of MSA were isolated and then cannulated to the two pipettes. Vascular diameters in response to the increased intraluminal pressure （from 0 mmHg to 150 mmHg, by 25 mmHg steps） of isolated MSA under no-flow conditions were recorded by a Pressure Myograph System both in physiologic salt solution （PSS） （active diameter, Da） and calcium-free PSS （passive diameter, Dp）. The myogenic tone was calculated by （Dp- Da）/Dp × 100%. The tail artery pressure and vascular myogenic tone in SHR rats were significantly higher than those of the CON rats. Before 24 weeks, the vascular myogenic tone of MSA in SHR group increased monotonically, but at the end of 32 weeks, the vascular myogenic tone decreased in comparison with that in 24-week group, but was significantly higher than that in CON group. The tail artery pressure in SHR group slowly increased monotonically with increasing weeks of age, and the tail arterial pressure in 32-week group remained significantly higher than that in 24-week group. Vascular myogenic tone may participate in the whole process of hypertension. Early in the development of hypertension, because of the compensatory role of vascular tone, the vascular function has been partially compensated, thus guaranteeing adequate blood supply to organs. Late in the development of hypertension, because of the decompensation of myogenic tone, the vascular function is damaged, leading to the occurrence of severe vascular disease.