Chorvatova A, Guyot A, Ojeda C, Rougier O, Bilbaut A
Université Claude Bernard Lyon I, UMR CNRS 5578, Villeurbanne, France.
J Membr Biol. 1998 Mar 1;162(1):39-50. doi: 10.1007/s002329900340.
The effects of angiotensin II (100 nM) on the electrical membrane properties of zona fasciculata cells isolated from calf adrenal gland were studied using the whole cell patch recording method. In current-clamp condition, angiotension II induced a biphasic membrane response which began by a transient hyperpolarization followed by a depolarization more positive than the control resting potential. These effects were abolished by Losartan (10(-5) M), an antagonist of angiotensin receptors of type 1. The angiotensin II-induced transient hyperpolarization was characterized in voltage-clamp condition from a holding potential of -10 mV. Using either the perforated or the standard recording method, a transient outward current accompanied by an increase of the membrane conductance was observed in response to the hormonal stimulation. This outward current consisted of an initial fast peak followed by an oscillating or a slowly decaying plateau current. In Cl(-)-free solution, the outward current reversed at -78.5 mV, a value close to EK. It was blocked by external TEA (20 mM) and by apamin (50 nM). In K(+)-free solution, the transient outward current, sensitive to Cl- channel blocker DPC (400 microM), reversed at -52 mV, a more positive potential than ECl. Its magnitude changed in the same direction as the driving force for Cl-. The hormone-induced transient outward current was never observed when EGTA (5 mM) was added to the pipette solution. The plateau current was suppressed in nominally CA(2+)-free solution (47% of cells) and was reversibly blocked by Cd2+ (300 microM) but not by nisoldipine (0.5-1 microM) which inhibited voltage-gated Ca2+ currents identified in this cell type. The present experiments show that the transient hyperpolarization induced by angiotensin II is due to Ca(2+)-dependent K+ and Cl- currents. These two membrane currents are co-activated in response to an internal increase of [Ca2+]i originating from intra- and extracellular stores.
采用全细胞膜片钳记录法，研究了血管紧张素II（100 nM）对从小牛肾上腺分离的束状带细胞电膜特性的影响。在电流钳条件下，血管紧张素II诱导了双相膜反应，开始时是短暂的超极化，随后是去极化，去极化后的电位比对照静息电位更正。这些效应被1型血管紧张素受体拮抗剂氯沙坦（10(-5) M）消除。血管紧张素II诱导的短暂超极化在电压钳条件下，从-10 mV的钳制电位进行表征。使用穿孔或标准记录方法，在激素刺激下观察到一个短暂的外向电流，伴随着膜电导的增加。该外向电流由一个初始的快速峰值和随后的振荡或缓慢衰减的平台电流组成。在无Cl(-)溶液中，外向电流在-78.5 mV处反转，该值接近EK。它被外部TEA（20 mM）和蜂毒明肽（50 nM）阻断。在无K(+)溶液中，对Cl-通道阻滞剂DPC（400 microM）敏感的短暂外向电流在-52 mV处反转，该电位比ECl更正。其幅度与Cl-的驱动力变化方向相同。当向移液管溶液中加入EGTA（5 mM）时，从未观察到激素诱导的短暂外向电流。在名义上无Ca(2+)的溶液中（47%的细胞），平台电流受到抑制，并被Cd2+（300 microM）可逆性阻断，但未被尼索地平（0.5-1 microM）阻断，尼索地平可抑制在这种细胞类型中鉴定出的电压门控Ca2+电流。本实验表明，血管紧张素II诱导的短暂超极化是由于Ca(2+)依赖性K+和Cl-电流。这两种膜电流是响应于源自细胞内和细胞外储存的[Ca2+]i的内部增加而共同激活的。
