Ishizawa M
Laboratory of Physiology, School of Allied Health Professions, Sapporo Medical College, Japan.
Prostaglandins. 1991 Dec;42(6):579-86. doi: 10.1016/0090-6980(91)90019-c.
The mechanical effects of 16-methyl analogues of PGE2, mainly 16,16-dimethyl PGE2, on circular and longitudinal muscles of the guinea-pig isolated proximal colon were investigated. In circular muscle strips, PGE2 100 nM produced an initial contraction followed by relaxation, while 16(R)-methyl PGE2 and 16,16-dimethyl PGE2 (1 nM - 1 microM) produced sustained contractions. In longitudinal muscle strips, PGE2 and 16-methyl analogues of PGE2 produced only contractions. The contractile responses of both muscle strips to 16,16-dimethyl PGE2 were not influenced by atropine or tetrodotoxin, indicating that these analogues act directly on the muscles, but were eliminated by the omission of extracellular Ca ions or in the presence of 1 mM lanthanum ions. However, verapamil, a Ca channel blocker, did not block the contractile response to the methyl analogues in circular muscle strips, although it completely inhibited the contractile response of longitudinal muscle strips. These results suggest that the contractile effect of 16-methyl analogues of PGE2 on the circular muscle may be due to an increased influx of Ca ions mainly via receptor-sensitive and partly voltage-sensitive Ca channels, while the contractile effect of the analogues on the longitudinal muscle may be due to an increase in influx of Ca ions via voltage-sensitive Ca channels.
研究了前列腺素E2（PGE2）的16-甲基类似物，主要是16,16-二甲基PGE2，对豚鼠离体近端结肠环行肌和纵行肌的机械效应。在环行肌条中，100 nM的PGE2引起初始收缩后松弛，而16（R）-甲基PGE2和16,16-二甲基PGE2（1 nM - 1 microM）引起持续收缩。在纵行肌条中，PGE2及其16-甲基类似物仅引起收缩。两种肌条对16,16-二甲基PGE2的收缩反应不受阿托品或河豚毒素的影响，表明这些类似物直接作用于肌肉，但通过去除细胞外钙离子或在1 mM镧离子存在下可消除该反应。然而，钙通道阻滞剂维拉帕米虽完全抑制纵行肌条的收缩反应，但不阻断环行肌条对甲基类似物的收缩反应。这些结果表明，PGE2的16-甲基类似物对环行肌的收缩作用可能主要是由于钙离子通过受体敏感性和部分电压敏感性钙通道的内流增加所致，而类似物对纵行肌的收缩作用可能是由于钙离子通过电压敏感性钙通道的内流增加所致。
