Pacaud P, Loirand G, Grégoire G, Mironneau C, Mironneau J
Laboratoire de Physiologie Cellulaire et Pharmacologie Moléculaire, URA Centre National de la Recherche Scientifique 1489, Université de Bordeaux II, France.
J Biol Chem. 1993 Feb 25;268(6):3866-72.
Single portal vein smooth muscle cells were voltage-clamped using the whole cell patch-clamp technique. Intracellular free Ca2+ concentration ([Ca2+]i) was simultaneously monitored using the fluorescence from the dye indo-1. Noradrenaline (NA, 10 microM) evoked a transient increase in [Ca2+]i, due to inositol 1,4,5-trisphosphate (InP3)-induced Ca2+ release, followed by a sustained increase in [Ca2+]i, caused by extracellular Ca2+ entry. This phase was maintained as long as NA was present and was never observed when the agonist was only briefly applied (3 s). Neither ryanodine, nor caffeine produced the Ca2+ influx whereas the complete depletion of intracellular Ca2+ pool in the absence of external Ca2+ allowed, when Ca2+ was readmitted, the activation of the Ca2+ entry which was used to replenish Ca2+ store. During NA stimulation, the Ca2+ entry was activated even if the Ca2+ pool had not been totally emptied. The Ca2+ entry pathway involved was blocked by Ni2+ and Mn2+, was not permeable to these ions, and was more sensitive to heparin than the InsP3-induced Ca2+ release. Thus, the complete depletion of Ca2+ store activates a Ca2+ influx which is modulated by NA such as in its presence, a partial depletion is enough to induce Ca2+ entry.
采用全细胞膜片钳技术对单根门静脉平滑肌细胞进行电压钳制。利用indo-1染料的荧光同时监测细胞内游离Ca2+浓度（[Ca2+]i）。去甲肾上腺素（NA，10微摩尔）引起[Ca2+]i短暂升高，这是由于肌醇1,4,5-三磷酸（InP3）诱导的Ca2+释放，随后[Ca2+]i持续升高，这是由细胞外Ca2+内流引起的。只要存在NA，这个阶段就会持续，而当激动剂仅短暂施加（3秒）时则从未观察到这种情况。ryanodine和咖啡因都不会产生Ca2+内流，而在没有外部Ca2+的情况下细胞内Ca2+池完全耗尽后，当重新引入Ca2+时，用于补充Ca2+储存的Ca2+内流会被激活。在NA刺激期间，即使Ca2+池没有完全排空，Ca2+内流也会被激活。所涉及的Ca2+内流途径被Ni2+和Mn2+阻断，对这些离子不通透，并且比InsP3诱导的Ca2+释放对肝素更敏感。因此，Ca2+储存的完全耗尽会激活一种Ca2+内流，这种内流会受到NA的调节，例如在其存在的情况下，部分耗尽就足以诱导Ca2+内流。
