Parfenova H, Hsu P, Leffler C W
Department of Physiology/Biophysics, University of Tennessee, Memphis.
J Pharmacol Exp Ther. 1995 Jan;272(1):44-52.
The effect of indomethacin on dilator prostanoid receptor-mediated cAMP formation was investigated using primary cultures of vascular smooth muscle cells from the newborn pig cerebral microvessels. Cerebral microvascular smooth muscle cells responded to dilator prostanoids (iloprost > PGE2) by increasing cAMP formation and release into the media (EC50 = 2 x 10(-8) M and 2 x 10(-7) M for iloprost and PGE2, respectively). Indomethacin inhibited iloprost- and PGE2-evoked increases in cAMP formation (IC50 = 10(-4) M) and release (IC50 = 10(-6) M) by microvascular smooth muscle cells (maximal inhibition 80-90%), whereas isoproterenol-induced cAMP formation was only slightly attenuated at the highest concentration of indomethacin used (10(-3) M). Aspirin was much less effective in inhibiting dilator prostanoid-induced cAMP formation and release by the cells. Direct analysis of prostacyclin receptor sites using [3H]iloprost as the ligand revealed saturable, high affinity (ED50 = 2 x 10(-8) M) and reversible binding to the membranes isolated from cerebrovascular smooth muscle cells. Indomethacin dose-dependently inhibited [3H]iloprost receptor binding (ID50 = 10(-4) M; maximal inhibition, 70%). The present data suggest that combination of highly effective inhibition of prostaglandin H synthase and receptor binding resulting in inhibition of dilator prostanoid-mediated cAMP formation in target cells may contribute to the increased efficacy of indomethacin compared with other prostaglandin H synthase inhibitors in blocking certain vasodilator responses associated with prostanoids.
利用新生猪脑微血管的血管平滑肌细胞原代培养物，研究了吲哚美辛对扩张型前列腺素受体介导的环磷酸腺苷（cAMP）形成的影响。脑微血管平滑肌细胞对扩张型前列腺素（依洛前列素＞前列腺素E2）有反应，通过增加cAMP的形成并释放到培养基中（依洛前列素和前列腺素E2的半数有效浓度分别为2×10⁻⁸M和2×10⁻⁷M）。吲哚美辛抑制微血管平滑肌细胞中依洛前列素和前列腺素E2引起的cAMP形成增加（半数抑制浓度=10⁻⁴M）和释放增加（半数抑制浓度=10⁻⁶M）（最大抑制率80 - 90%），而异丙肾上腺素诱导的cAMP形成在所用吲哚美辛的最高浓度（10⁻³M）时仅略有减弱。阿司匹林在抑制细胞中扩张型前列腺素诱导的cAMP形成和释放方面效果要差得多。使用[³H]依洛前列素作为配体对前列环素受体位点进行直接分析，结果显示其与从脑血管平滑肌细胞分离的膜具有可饱和、高亲和力（半数有效剂量=2×10⁻⁸M）且可逆的结合。吲哚美辛剂量依赖性地抑制[³H]依洛前列素受体结合（半数抑制剂量=10⁻⁴M；最大抑制率70%）。目前的数据表明，与其他前列腺素H合酶抑制剂相比，吲哚美辛在阻断某些与前列腺素相关的血管舒张反应方面疗效增加，可能是由于其对前列腺素H合酶和受体结合的高效抑制相结合，从而抑制了靶细胞中扩张型前列腺素介导的cAMP形成。
