Wang Jian, Laurier Lisanne G, Sims Stephen M, Preiksaitis Harold G
Department of Medicine, The University of Western Ontario, London, Ontario N6A 4V2, Canada.
Am J Physiol Gastrointest Liver Physiol. 2003 Jun;284(6):G1074-83. doi: 10.1152/ajpgi.00227.2002.
Transient receptor potential channel (TRPC) genes encode Ca(2+)-permeable channels mediating capacitative Ca(2+) entry (CCE), which maintains intracellular Ca(2+) stores. We compared TRPC gene expression and CCE in human esophageal body (EB) and lower esophageal sphincter (LES), because these smooth muscles have distinct contractile functions that are likely associated with different Ca(2+) regulatory mechanisms. Circular layer smooth muscle cells were grown in primary culture. Transcriptional expression of TRPC genes was compared by semiquantitative RT-PCR. CCE was measured by fura 2 Ca(2+) fluorescence after blockade of sarcoplasmic reticulum Ca(2+)-ATPase with thapsigargin. mRNA for TRPC1, TRPC3, TRPC4, TRPC5, and TRPC6 was identified in EB and LES. TRPC3 and TRPC4 were more abundant in LES than EB. Basal concentration of free intracellular Ca(2+) (Ca(2+)) was similar in cells from LES (138 +/- 8 nmol/l) and EB (110 +/- 6 nmol/l) and increased with ACh (10 micromol/l; 650 +/- 28 and 590 +/- 21 nmol/l, respectively). With zero Ca(2+) in bath, thapsigargin (2 micromol/l) increased Ca(2+) more in LES (550 +/- 22 nmol/l) than EB (250 +/- 15 nmol/l, P < 0.001). Subsequent external application of 1 mmol/l Ca(2+) increased Ca(2+) more in LES (585 +/- 35 nmol/l) than EB (295 +/- 21 nmol/l, P < 0.001), indicating enhanced CCE in LES. This demonstrates CCE and TRPC transcriptional expression in human esophageal smooth muscle. In LES cells, enhanced CCE and expression of TRPC3 and TRPC4 may contribute to the physiological characteristics that distinguish LES from EB.
瞬时受体电位通道（TRPC）基因编码介导容量性钙内流（CCE）的钙通透性通道，该过程维持细胞内钙库。我们比较了人食管体（EB）和食管下括约肌（LES）中TRPC基因的表达及CCE情况，因为这些平滑肌具有不同的收缩功能，可能与不同的钙调节机制相关。环形肌层平滑肌细胞进行原代培养。通过半定量逆转录聚合酶链反应（RT-PCR）比较TRPC基因的转录表达。在用毒胡萝卜素阻断肌浆网钙-ATP酶后，用fura 2钙荧光法测量CCE。在EB和LES中鉴定出了TRPC1、TRPC3、TRPC4、TRPC5和TRPC6的信使核糖核酸（mRNA）。TRPC3和TRPC4在LES中比在EB中更丰富。LES细胞（138±8纳摩尔/升）和EB细胞（110±6纳摩尔/升）内游离钙（[Ca²⁺]i）的基础浓度相似，且在乙酰胆碱（10微摩尔/升）作用下升高（分别为650±28和590±21纳摩尔/升）。在浴液中无钙时，毒胡萝卜素（2微摩尔/升）使LES细胞内[Ca²⁺]i升高幅度（550±22纳摩尔/升）大于EB细胞（250±15纳摩尔/升，P<0.001）。随后外部施加1毫摩尔/升钙使LES细胞内[Ca²⁺]i升高幅度（585±35纳摩尔/升）大于EB细胞（295±21纳摩尔/升，P<0.001），表明LES中的CCE增强。这证明了人食管平滑肌中的CCE和TRPC转录表达。在LES细胞中，增强的CCE以及TRPC3和TRPC4的表达可能有助于LES区别于EB的生理特性。
