Sevy N, Snape W J
Department of Medicine, Harbor-UCLA Medical Center, Torrance 90502.
Am J Physiol. 1988 Jun;254(6 Pt 1):G808-13. doi: 10.1152/ajpgi.1988.254.6.G808.
Studies were performed on proximal taenia coli and distal circular muscle from the rabbit to determine if the source of Ca2+ required for bethanechol stimulation of contraction was similar after permeabilizing the tissues with saponin. The EC50 for Ca2+ stimulation of contraction was pCa 6.1 +/- 0.1 for both tissues. The peak response occurred at pCa 4.5. The addition of 1 microM calmodulin did not alter the Ca2+ EC50 or the peak response. Caffeine (20 mM) stimulated contraction of both taenia coli and distal circular muscle. The caffeine-stimulated contractile response was threefold greater in the taenia than in the distal circular muscle (P less than 0.05). Perfusion of thin strips of colonic muscle with buffer, containing 10(-7) M Ca2+, reduced the amplitude of bethanechol-stimulated contraction. The perfusion time to reduce the contraction by 50% was greater in the proximal muscle (2.4 +/- 0.1 min) than in the distal muscle (1.1 +/- 0.5 min) (P less than 0.001). These data suggest that 1) the intracellular Ca2+ concentration necessary for contraction is similar in the proximal and distal colon and 2) the intracellular Ca2+ stores appear to be greater in proximal taenia coli compared with distal circular muscle.
对兔近端结肠带和远端环行肌进行了研究，以确定在用皂角苷使组织通透后，氨甲酰甲胆碱刺激收缩所需的Ca2+来源是否相似。两种组织中Ca2+刺激收缩的EC50为pCa 6.1±0.1。峰值反应出现在pCa 4.5。添加1 microM钙调蛋白不会改变Ca2+ EC50或峰值反应。咖啡因（20 mM）刺激结肠带和远端环行肌收缩。咖啡因刺激的收缩反应在结肠带中比在远端环行肌中大三倍（P<0.05）。用含10(-7)M Ca2+的缓冲液灌注结肠肌薄条，可降低氨甲酰甲胆碱刺激的收缩幅度。近端肌肉中使收缩降低50%的灌注时间（2.4±0.1分钟）比远端肌肉（1.1±0.5分钟）长（P<0.001）。这些数据表明：1）近端和远端结肠收缩所需的细胞内Ca2+浓度相似；2）与远端环行肌相比，近端结肠带的细胞内Ca2+储备似乎更多。
