Coyne M D, Rodriguez O, Wilson Y, Wang G, Lemos J R
Department of Biological Sciences, Wellesley College, MA 02181, USA.
Endocr Res. 1997 Nov;23(4):245-75. doi: 10.1080/07435809709031857.
In this report we use both whole cell and perforated patch clamp recording techniques to characterize calcium and potassium channels in Y-1 adrenocortical cells in order to assess their responsiveness to ACTH. Both transient and long-lasting components of an inward calcium current were identified which were similar to T and L-type Ca2+ currents. With Ba2+ as the charge carrier, the transient current activated at voltages more hyperpolarized than -50 mV with V1/2 for activation at -78.1 mV, and for steady state inactivation at -52.3 mV. The L-type current activated at -20 mV, with a V1/2 for activation at -29.9 mV and steady state inactivation at -44.2 mV. Under perforated patch conditions the response was shifted to more depolarized voltages. Both currents were responsive to agents which usually affect T- or L-type Ca2+ currents. The transient current was completely blocked by 50 microM lanthanum or 200 microM nickel and partially blocked by 300 mM amiloride. Cadmium (100 microM) and nifedipine (300 nM) completely blocked the long-lasting current while omega-conotoxin GVIA (1992 nM) inhibited the current by only 20-25%. The agonist, Bay K 8644 was stimulatory at 50 nM. Both transient and sustained outward potassium currents similar to A-type and delayed rectifier currents, respectively, were present. The transient current demonstrated fast activation at voltages more positive than -10 mV, inactivation with continued depolarization and steady state inactivation at V1/2 = -50 mV. The sustained current activated rapidly and had minimal inactivation with continued depolarization. The transient current was blocked by 5 mM 4AP and the sustained by 25 mM TEA. While Y-1 cells contain both calcium and potassium currents similar to those found in other adrenocortical cells, none of the currents were affected by ACTH or AII, secretagogues which stimulate steroidogenesis. These data, combined with the inability of both Ca2+ and K+ channel blockers to alter ACTH-induced steroidogenesis as reported earlier, suggests that neither calcium nor potassium currents are responsive to ACTH in Y-1 cells.
在本报告中，我们使用全细胞和穿孔膜片钳记录技术来表征Y-1肾上腺皮质细胞中的钙通道和钾通道，以评估它们对促肾上腺皮质激素（ACTH）的反应性。我们识别出内向钙电流的瞬时成分和持久成分，它们分别类似于T型和L型Ca2+电流。以Ba2+作为载流子，瞬时电流在比-50 mV更超极化的电压下激活，激活的半电压（V1/2）为-78.1 mV，稳态失活的半电压为-52.3 mV。L型电流在-20 mV时激活，激活的半电压为-29.9 mV，稳态失活的半电压为-44.2 mV。在穿孔膜片钳条件下，反应向更正的电压偏移。两种电流都对通常影响T型或L型Ca2+电流的试剂有反应。瞬时电流被50 μM镧或200 μM镍完全阻断，被300 mM阿米洛利部分阻断。镉（100 μM）和硝苯地平（300 nM）完全阻断持久电流，而ω-芋螺毒素GVIA（1992 nM）仅使电流抑制20 - 25%。激动剂Bay K 8644在50 nM时具有刺激作用。分别存在类似于A型和延迟整流型电流的瞬时外向钾电流和持续外向钾电流。瞬时电流在比-10 mV更正的电压下快速激活，随着持续去极化而失活，稳态失活的半电压（V1/2）为-50 mV。持续电流快速激活，随着持续去极化失活最小。瞬时电流被5 mM 4-氨基吡啶（4AP）阻断，持续电流被25 mM四乙铵（TEA）阻断。虽然Y-1细胞含有与其他肾上腺皮质细胞中发现的类似的钙电流和钾电流，但这些电流均不受ACTH或血管紧张素II（AII）的影响，ACTH和AII是刺激类固醇生成的促分泌素。这些数据，结合如前所述Ca2+和K+通道阻滞剂均无法改变ACTH诱导的类固醇生成这一情况，表明在Y-1细胞中钙电流和钾电流均对ACTH无反应。
