内皮素对麻醉大鼠动脉压力感受器反射的调制作用

在27只隔离灌流颈动脉窦区的麻醉大鼠,观察了内皮素（ET-1）对动脉压力感受器反射的调制作用。结果如下：（1）在颈动脉窦区灌流1nmol／L的ET-1时,压力感受器机能曲线向左下方移位,曲线的最大斜率（PS）由0.40±0.02增至0.51±0.02kPa／kPa（P＜0.01）,压力感受器反射性血压下降幅度（RD）由5.66±0.23增至6.76±0.22kPa（P＜0.01）。由此提示,这一剂量的FT-1对压力感受器反射有易化作用。（2）用10nmol／L的ET-1灌流时,压力感受器机能曲线则向右上方移位,PS降至0.28±0.01kPa／kPa（P＜0.01）,RD降至4．16±0.19kPa（P＜0.01）;100nmol／L的ET-1可使压力感受器机能曲线向右上方移位更为明显,PS降至0.19±0.03kPa（P＜0.001）,RD进一步降至3.33±0.38kPa（P＜0.001）。这些结果表明,上述两种剂量的ET-1对压力感受器反射有抑制作用。（3）ETA受体选择性阻断剂BQ123（0.15μmol／L）可以阻断ET-1（10nmol／L）对压力感受器反射的抑制效应。（4）预先灌流KATP通道阻断剂格列苯脲（10μmol／L）,也可阻断ET-1的效应。综上所述,ET-1对压力感受器反射有双重效应,低剂量时有易化作用,而较高剂量时则有抑制作用,后一作用由ET-1型受体介导并有KATP通道的参与。

Modulatory effects of endothelin on carotid baroreflex in anesthetized rats

Modulatory effects of endothelin (ET) on carotid baroreflex were examined in 27 anesthetized rats with isolated carotid sinus perfusion. The results obtained were as follows: (1) By perfusing with 1 nmol/L ET-1, the functional curve of carotid baroreflex (FCCB) was shifted to the left and downward with an increase in its peak slope (PS) from 0.40 +/- 0.02 to 0.51 +/- 0.02 kPa/kPa (P < 0.01), while the reflex decrease of mean arterial pressure (RD) was increased from 5.66 +/- 0.23 to 6.76 +/- 0.22 kPa (P < 0.01). The above results indicated that this dose of ET-1 facilitated the carotid baroreflex. (2) On the contrary, by perfusing with 10 nmol/L of ET-1, FCCB was shifted to the right and upward with a decrease of PS to 0.28 +/- 0.01 kPa/kPa (P < 0.01), while RD was decreased to 4.16 +/- 0.19 kPa (P < 0.01). In response to perfusion with 100 nmol/L ET-1, FCCB was further shifted to the right and upward with a marked decrease of PS to 0.19 +/- 0.03 kPa/kPa (P < 0.001), and RD was conspicuously decreased to 3.33 +/- 0.38 kPa (P < 0.001). These results showed that ET-1 at the doses of 10 or 100 nmol/L exerted an inhibitory action on baroreflex. (3) Selective ETA receptor blocker BQ123 (0.15 mumol/L) might abolish the effects of ET-1 (10 nmol/L) on baroreflex. (4) Preperfusing with KATP channel antagonist glibenclamide (10 mumol/L) could also eliminated the effects of ET-1. Taken together, it is suggested that ET-1 exerts a dual effects on baroreflex, being facilitatory at lower dose and inhibitory at higher dose. The latter effect is mediated by ETA receptor, in which KATP channels may be involved.