Hwang T L, Wu C C, Teng C M
Pharmacological Institute, College of Medicine, National Taiwan University, Taipei.
Br J Pharmacol. 1998 Nov;125(6):1158-63. doi: 10.1038/sj.bjp.0702181.
To clarify further the role of cyclic GMP in mediating the relaxant response in guinea-pig trachea induced by sodium nitroprusside (SNP), the effects of soluble guanylyl cyclase inhibitors, methylene blue and 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one (ODQ) on SNP-induced muscle relaxation and cyclic GMP accumulation were determined. SNP (0.3-100 microM) evoked a concentration-dependent relaxation of guinea-pig isolated tracheas precontracted with 0.3 microM carbachol. Preincubation of the preparations with methylene blue (10, 30 and 100 microM) resulted in a slight but concentration-dependent prevention of the relaxant response to SNP. In contrast, the relaxation to SNP was extensively prevented by 3 microM ODQ and almost abolished by 10 microM ODQ. SNP (30 microM) induced a significant elevation of cyclic GMP accumulation (from 1.34+/-0.14 to 5.39+/-0.28 pmol mg(-1) protein, n= 5; P<0.001), which was partially attenuated by 100 microM methylene blue (3.11+/-0.51 pmol mg(-1) protein, n=5; P<0.05), whereas completely abolished by 10 microM ODQ (1.31+/-0.28 pmol mg(-1) protein, n = 5; P<0.001). Methylene blue, but not ODQ and Nomega-nitro-L-arginine methyl ester (L-NAME), caused a concentration-dependent contraction in the tracheal preparation. The tension produced by 100 microM methylene blue was 41.8+/-4.3% (0.3 microM carbachol as 100%; n = 12). Moreover, the non-selective muscarinic receptor antagonist atropine and the M3-selective antagonist 4-diphenylacetoxy-N-methylpiperidine methiodine greatly inhibited the contractile effect evoked by methylene blue (100 microM). In conclusion, this study provides substantial evidence that SNP-induced muscle relaxation in guinea-pig trachea is completely via a cyclic GMP-dependent mechanism. Furthermore, ODQ, but not methylene blue, will likely become an important tool in differentiating between cyclic GMP-dependent and -independent effects of nitric oxide.
为了进一步阐明环鸟苷酸（cGMP）在介导硝普钠（SNP）诱导的豚鼠气管舒张反应中的作用，测定了可溶性鸟苷酸环化酶抑制剂亚甲蓝和1H-[1,2,4]恶二唑并[4,3,-a]喹喔啉-1-酮（ODQ）对SNP诱导的肌肉舒张和cGMP积累的影响。SNP（0.3 - 100 μM）可引起预先用0.3 μM卡巴胆碱预收缩的豚鼠离体气管浓度依赖性舒张。将标本与亚甲蓝（10、30和100 μM）预孵育导致对SNP舒张反应有轻微但浓度依赖性的抑制。相反，3 μM ODQ可广泛抑制对SNP的舒张反应，10 μM ODQ几乎完全消除该反应。SNP（30 μM）可使cGMP积累显著升高（从1.34±0.14升高至5.39±0.28 pmol mg⁻¹蛋白，n = 5；P<0.001），100 μM亚甲蓝可部分减弱该升高（3.11±0.51 pmol mg⁻¹蛋白，n = 5；P<0.05），而10 μM ODQ可完全消除该升高（1.31±0.28 pmol mg⁻¹蛋白，n = 5；P<0.001）。亚甲蓝而非ODQ和Nω-硝基-L-精氨酸甲酯（L-NAME）可引起气管标本浓度依赖性收缩。100 μM亚甲蓝产生的张力为41.8±4.3%（以0.3 μM卡巴胆碱为100%；n = 12）。此外，非选择性毒蕈碱受体拮抗剂阿托品和M3选择性拮抗剂4-二苯基乙酰氧基-N-甲基哌啶甲碘化物可极大地抑制亚甲蓝（100 μM）引起的收缩效应。总之，本研究提供了充分证据表明SNP诱导的豚鼠气管肌肉舒张完全通过cGMP依赖性机制实现。此外，ODQ而非亚甲蓝可能会成为区分一氧化氮的cGMP依赖性和非依赖性效应的重要工具。
