Johnston L, Sergeant G P, Hollywood M A, Thornbury K D, McHale N G
Smooth Muscle Research Centre, Dundalk Institute of Technology, Dundalk, County Louth, Ireland.
J Physiol. 2005 Jun 1;565(Pt 2):449-61. doi: 10.1113/jphysiol.2004.078097. Epub 2005 Mar 10.
Measurements were made (using fast confocal microscopy) of intracellular Ca2+ levels in fluo-4 loaded interstitial cells isolated from the rabbit urethra. These cells exhibited regular Ca2+ oscillations which were associated with spontaneous transient inward currents recorded under voltage clamp. Interference with D-myo-inositol 1,4,5-trisphosphate (IP3) induced Ca2+ release using 100 microm 2-aminoethoxydiphenyl borate, and the phospholipase C (PLC) inhibitors 2-nitro-4-carboxyphenyl N,N-diphenylcarbamate and U73122 decreased the amplitude of spontaneous oscillations but did not abolish them. However, oscillations were abolished when ryanodine receptors were blocked with tetracaine or ryanodine. Oscillations ceased in the absence of external Ca2+, and frequency was directly proportional to the external Ca2+ concentration. Frequency of Ca2+ oscillation was reduced by SKF-96365, but not by nifedipine. Lanthanum and cadmium completely blocked oscillations. These results suggest that Ca2+ oscillations in isolated rabbit urethral interstitial cells are initiated by Ca2+ release from ryanodine-sensitive intracellular stores, that oscillation frequency is very sensitive to the external Ca2+ concentration and that conversion of the primary oscillation to a propagated Ca2+ wave depends upon IP3-induced Ca2+ release.
使用快速共聚焦显微镜对从兔尿道分离的负载fluo-4的间质细胞内的Ca2+水平进行了测量。这些细胞表现出规则的Ca2+振荡，这与在电压钳制下记录到的自发瞬态内向电流相关。使用100微摩尔的2-氨基乙氧基二苯硼酸盐干扰D-肌醇1,4,5-三磷酸（IP3）诱导的Ca2+释放，以及磷脂酶C（PLC）抑制剂2-硝基-4-羧基苯基N,N-二苯基氨基甲酸盐和U73122降低了自发振荡的幅度，但并未消除它们。然而，当用丁卡因或ryanodine阻断ryanodine受体时，振荡被消除。在没有外部Ca2+的情况下振荡停止，并且频率与外部Ca2+浓度成正比。Ca2+振荡的频率被SKF-96365降低，但未被硝苯地平降低。镧和镉完全阻断了振荡。这些结果表明，分离的兔尿道间质细胞中的Ca2+振荡是由ryanodine敏感的细胞内储存释放Ca2+引发的，振荡频率对外部Ca2+浓度非常敏感，并且初级振荡向传播的Ca2+波的转换取决于IP3诱导的Ca2+释放。
