钙稳态失衡在致结肠平滑肌收缩性改变中的作用

目的　探讨应激大鼠结肠平滑肌收缩时细胞内外钙离子 (Ca2 +)利用异常、细胞内钙稳态失衡在导致其收缩性改变中的作用。方法　建立寒冷 束缚应激大鼠排便异常的动物模型 ;测定离体结肠环形平滑肌收缩张力 ;差速离心制备结肠平滑肌肌浆网 ,测定肌浆网Ca2 + ATP酶活性。结果　应激大鼠结肠平滑肌收缩活性明显增强 ,并受Ca2 +通道阻滞剂显著抑制。应激大鼠结肠平滑肌肌浆网Ca2 + ATP酶活性降低 5 6 % (P <0 .0 5 )。结论　应激大鼠结肠环形平滑肌收缩活性显著增强 ,可能和肌细胞收缩时细胞外Ca2 +内流增加 ,肌浆网贮存Ca2 +释放减少、Ca2 + ATP酶活性降低等因素导致细胞内钙稳态失衡有关

Alteration of Ca2+ mobilization and increased circular muscle contractility in colon of stressed rats

OBJECTIVE: To investigate relationship between the cold-restraint stress induced colonic circular muscle contractility disorder and calcium-handling properties alteration of the affected muscle in rats. METHODS: Stress was conducted on rats to induce the fecal pellet output increased. Contractile responses to acetylcholine (Ach), KCl, and NaF were determined for colonic circular muscle. To investigate Ca(2+) mobilization, effects of Ca(2+)-free solution, high concentration of extracellular Ca(2+), and pinaverium bromide on the contractility of colon were determined. Prepared sarcoplasmic reticular (SR) of colonic muscle by differential centrifugation and measured Ca(2+)-ATPase activity with colorimetric assay. RESULTS: In stressed rats, contractile responses of colonic circular muscle to Ach, KCl, and NaF increased significantly; the contraction was more sensitive to high concentration of extracellular Ca(2+) than control. In Ca(2+)-free solution, contractions were significantly suppressed in both groups. Pinaverium dose-dependently blocked contractions acting with different sensitivity on the two preparations. The Ca(2+)-ATPase activity of the SR in stress was lower than control. CONCLUSIONS: Cold- restraint stress caused a marked increase in the contractility of the colonic circular muscle in rats. Stressed rats' colonic muscle shows an alteration in the homeostasis of intracellular Ca(2+), with appears to be the consequence of increased influx of extracellular Ca(2+), decreased release of intracellular stores of Ca(2+) and a decreased Ca(2+)-ATPase activity of the SR.