Siegel G, Carl A, Adler A, Stock G
Institute of Physiology, Biophysical Research Group, Free University of Berlin, Germany.
Eicosanoids. 1989;2(4):213-22.
The present contribution deals with the electro- and tracerphysiological correlations to vasodilatation observed under prostacyclin or O2 deficiency. Because of the extreme chemical instability of native PGI2, we used iloprost, a stable carbacyclin analogue. At concentrations between 10(-9) and 10(-6) mol/l, iloprost hyperpolarized the resting membrane of normal tone (V = -63.4 mV) and noradrenaline predepolarized vascular smooth muscle cells (V = -55.2 mV) of the canine carotid artery by 7.4 and 16.9 mV, respectively, in a concentration-dependent manner. Correspondingly, the isometric tension was decreased. In both experimental series, the half-maximal effect was attained at a concentration of 2 x 10(-8) mol/l. The coupling ratios developed tension versus membrane potential were 1.079 mV/mN in normal tone and noradrenaline treated preparations. Hyperpolarization and relaxation in the latter group, however, were much larger for the same iloprost concentrations. 42K+ efflux was stimulated by 250% with iloprost (10(-6) mol/l), whereas 24Na+ efflux was increased only by 50%. This resulted in an augmentation of K+ permeability by 340% and of Na+ permeability by 40%, respectively. The ratio PK/PNa rose from 16 to 49 with iloprost. These results lead to the conclusion that iloprost should be classified as a K+ channel opener.
本研究探讨了在前列环素或缺氧条件下观察到的血管舒张与电生理及示踪生理之间的相关性。由于天然前列环素（PGI2）化学性质极不稳定，我们使用了依洛前列素，一种稳定的卡前列素类似物。在浓度为10^(-9)至10^(-6) mol/l之间时，依洛前列素可使犬颈动脉正常张力下的静息膜（V = -63.4 mV）超极化7.4 mV，使去甲肾上腺素预去极化的血管平滑肌细胞（V = -55.2 mV）超极化16.9 mV，且呈浓度依赖性。相应地，等长张力降低。在两个实验系列中，浓度为2×10^(-8) mol/l时达到最大效应的一半。在正常张力和去甲肾上腺素处理的标本中，张力与膜电位的耦合比为1.079 mV/mN。然而，对于相同浓度的依洛前列素，后一组的超极化和舒张程度要大得多。依洛前列素（10^(-6) mol/l）可使42K+外流增加250%，而24Na+外流仅增加50%。这分别导致K+通透性增加340%，Na+通透性增加40%。依洛前列素作用下PK/PNa比值从16升至49。这些结果得出结论，依洛前列素应归类为钾通道开放剂。
