Nakamura Eri, Yokoi Tsuyoshi, Fukuta Hiroyasu, Iida Takao, Tanaka Yasuo, Yamamoto Yoshimichi, Suzuki Hikaru
Department of Physiology, Nagoya City University, Mizuho-ku, Nagoya, Japan.
J Smooth Muscle Res. 2009 Aug;45(4):149-66. doi: 10.1540/jsmr.45.149.
Effects of hypoxic solution (O(2) tension, 161 +/- 11 mmHg) on electrical responses of the membrane (slow waves), intracellular Ca(2+)-responses measured by Fura-2 fluorescence (Ca-transients) and isometric mechanical responses (phasic contraction) were observed in circular smooth muscles isolated from the guinea-pig stomach antrum. In normoxic solution (O(2) tension, 362 +/- 28 mmHg), muscle cells generated slow waves spontaneously, and switching to hypoxic solution caused an increase in frequency and decrease in duration of slow waves, with no significant change in the resting membrane potential. Hypoxia also reduced the amplitude and duration and increased the frequency of Ca-transients. The increase in frequency of slow waves by hypoxia was prevented by cyclopiazonic acid (CPA) but not by carbonyl cyanide m-chlorophenyl-hydrazone (CCCP), potassium cyanide (KCN) or low-Ca solution. The reduction by hypoxia of the duration of slow waves was prevented by CCCP or KCN but not by CPA or low-Ca solution. Hypoxia resulted in an increase in frequency and decrease in amplitude of phasic contractions, and the changes were prevented by CPA but not by CCCP. These results suggested that in antrum smooth muscle tissues, the increase in frequency of spontaneous activity by hypoxia is related to the enhanced function of the CPA-sensitive internal Ca-stores in pacemaker cells, while the inhibition in amplitude of phasic contractions by hypoxia may be mainly related to the decrease in Ca(2+) release from the CPA-sensitive internal stores in smooth muscle cells. It is concluded that in hypoxic solution, the function of internal Ca(2+) stores is enhanced in ICC-MY and is inhibited in smooth muscle cells in the guinea-pig stomach antrum.
在从豚鼠胃窦分离的环形平滑肌中，观察了缺氧溶液（氧张力，161±11mmHg）对膜电反应（慢波）、通过Fura-2荧光测量的细胞内钙反应（钙瞬变）和等长机械反应（相性收缩）的影响。在常氧溶液（氧张力，362±28mmHg）中，肌肉细胞自发产生慢波，切换到缺氧溶液会导致慢波频率增加和持续时间缩短，静息膜电位无显著变化。缺氧还降低了钙瞬变的幅度和持续时间，并增加了其频率。缺氧引起的慢波频率增加可被环匹阿尼酸（CPA）阻止，但不能被羰基氰化物间氯苯腙（CCCP）、氰化钾（KCN）或低钙溶液阻止。缺氧引起的慢波持续时间缩短可被CCCP或KCN阻止，但不能被CPA或低钙溶液阻止。缺氧导致相性收缩频率增加和幅度减小，这些变化可被CPA阻止，但不能被CCCP阻止。这些结果表明，在胃窦平滑肌组织中，缺氧引起的自发活动频率增加与起搏细胞中CPA敏感的细胞内钙库功能增强有关，而缺氧引起的相性收缩幅度抑制可能主要与平滑肌细胞中CPA敏感的细胞内钙库释放钙减少有关。得出的结论是，在缺氧溶液中，豚鼠胃窦中ICC-MY的细胞内钙库功能增强，而平滑肌细胞中的功能受到抑制。
