Pierce G N, Langer G A, Wright G B, Kutryk M J
Department of Medicine, American Heart Association, Los Angeles.
J Mol Cell Cardiol. 1989 Sep;21(9):889-99. doi: 10.1016/0022-2828(89)90757-8.
Calcium exchange was measured in enzymatically isolated, cultured smooth muscle cells from the rabbit thoracic aorta. Cells were grown to confluence in monolayer on scintillator discs which were then inserted into a modified flow cell/spectrometer to measure 45Ca exchange in a continuous, on-line manner. This also allowed us to measure rapid movements of cellular Ca2+ without solubilizing the cells. Two components of Ca2+ exchange were detected: a La3+-displaceable, rapidly exchangeable fraction (t 1/2 = 15.6 s) and a slowly exchangeable fraction (t 1/2 = 34.5 min). The La3+ displaceable, rapidly exchangeable Ca2+ fraction represented 57 to 61% of the total exchangeable Ca2+. Multiple passaging of cells did not after the Ca2+ flux characteristics. Low Na+ perfusion increased smooth muscle cell Ca2+ flux by 6.71 mmol/kg dry weight. This increase was localized to both the rapidly and slowly exchangeable Ca2+ compartments. Ouabain, an inhibitor of the plasmalemmal Na+ -K+ pump, also increased net uptake of 45Ca. The results demonstrate that approximately 60% of exchangeable Ca2+ of smooth muscle cells is very rapidly exchangeable (t 1/2 less than 16 s). The results stress the importance of measuring 45Ca2+ movements in an on-line, continuous manner in order to ensure detection of the majority of total exchangeable Ca2+ in smooth muscle cells.
在从兔胸主动脉酶解分离并培养的平滑肌细胞中测量钙交换。细胞在闪烁体圆盘上单层生长至汇合，然后将圆盘插入改良的流动池/光谱仪中，以连续、在线方式测量⁴⁵Ca交换。这也使我们能够在不解离细胞的情况下测量细胞Ca²⁺的快速移动。检测到Ca²⁺交换的两个组分：一个可被La³⁺置换的快速交换部分（t₁/₂ = 15.6秒）和一个缓慢交换部分（t₁/₂ = 34.5分钟）。可被La³⁺置换的快速交换Ca²⁺部分占总可交换Ca²⁺的57%至61%。细胞多次传代后，Ca²⁺通量特性未发生改变。低钠灌注使平滑肌细胞Ca²⁺通量增加6.71 mmol/kg干重。这种增加同时发生在快速和缓慢交换的Ca²⁺区室。哇巴因是质膜Na⁺-K⁺泵的抑制剂，也增加了⁴⁵Ca的净摄取量。结果表明，平滑肌细胞中约60%的可交换Ca²⁺可非常快速地交换（t₁/₂小于16秒）。结果强调了以在线、连续方式测量⁴⁵Ca²⁺移动的重要性，以确保检测到平滑肌细胞中大部分的总可交换Ca²⁺。
