A. Rocha-Sousa, Department of Physiology, Faculty of Medicine, Porto, Portugal.
Physiol Res. 2009;58(6):835-842. doi: 10.33549/physiolres.931365. Epub 2008 Dec 17.
Effects of ET(B) receptor stimulation and its subcellular pathways were evaluated in carbachol pre-contracted rabbit iris sphincter muscles (n=51). ET(B) stimulation with sarafotoxin (SRTX-c; 10(-10)-10(-6) M) was tested in the absence (n=7) or presence of 10(-5) M of: BQ-788 (ET(B2) receptor antagonist; n=6), L-NA (NOS inhibitor; n=7) or indomethacin (cyclooxygenase inhibitor; n=10). Effects of ET(B) stimulation by endothelin-1 (ET-1; 10(-10)-10(-7) M) in the presence of an ET(A) receptor antagonist (BQ-123; 10(-5) M; n=7) and of ET(B1) stimulation by IRL-1620 (10(-10)-10(-7) M; n=7) were also tested. Finally, the effects of SRTX-c (10(-9)-10(-7) M) in electric field stimulation (EFS) contraction were evaluated (n=7). ET(B) receptor stimulation by SRTX-c or ET-1 in presence of BQ-123 promoted a concentration-dependent relaxation of the rabbit iris sphincter muscle by 10.8+/-2.0% and 9.4+/-1.8%, respectively. This effect was blocked by BQ-788 (-2.3+/-2.0 %), L-NA (4.5+/-2.3 %) or indomethacin (2.3+/-2.9 %). Selective ET(B1) stimulation by IRL-1620 did not relax the iris sphincter muscle (0.9+/-5.4 %). EFS elicited contraction was not altered by SRTX-c. In conclusion, ET(B) receptor stimulation relaxes the carbachol precontracted iris sphincter muscle, an effect that is mediated by the ET(B2) receptor subtype, through NO and the release of prostaglandins.
研究了 ET(B) 受体刺激及其亚细胞途径对兔虹膜括约肌（n=51）的影响。在不存在（n=7）或存在 10(-5) M 的情况下测试了 SRTX-c（10(-10)-10(-6) M）对 ET(B) 的刺激：BQ-788（ET(B2)受体拮抗剂；n=6）、L-NA（NOS 抑制剂；n=7）或吲哚美辛（环氧化酶抑制剂；n=10）。还测试了 ET-1（10(-10)-10(-7) M）在 ET(A) 受体拮抗剂（BQ-123；10(-5) M；n=7）存在下对 ET(B) 的刺激以及 IRL-1620（10(-10)-10(-7) M）对 ET(B1) 的刺激的影响。最后，评估了 SRTX-c（10(-9)-10(-7) M）在电场刺激（EFS）收缩中的作用（n=7）。SRTX-c 或 ET-1 在 BQ-123 存在下刺激 ET(B) 受体可分别使兔虹膜括约肌松弛 10.8+/-2.0%和 9.4+/-1.8%，呈浓度依赖性。这种作用被 BQ-788（-2.3+/-2.0%）、L-NA（4.5+/-2.3%）或吲哚美辛（2.3+/-2.9%）阻断。IRL-1620 对选择性 ET(B1) 的刺激不能使虹膜括约肌松弛（0.9+/-5.4%）。EFS 引起的收缩不受 SRTX-c 影响。总之，ET(B) 受体刺激可松弛已用卡巴胆碱预收缩的虹膜括约肌，这种作用是通过 ET(B2) 受体亚型介导的，通过 NO 和前列腺素的释放来实现的。
