Michels Guido, Er Fikret, Eicks Michael, Herzig Stefan, Hoppe Uta C
Department of Internal Medicine III, University of Cologne, Kerpener Strasse 62, 50937 Cologne, Germany.
Endocrinology. 2006 Nov;147(11):5160-9. doi: 10.1210/en.2006-0186. Epub 2006 Jul 27.
In the cardiovascular system, T-type calcium channels play an important role for the intracellular calcium homeostasis and spontaneous pacemaker activity and are involved in the progression of structural heart diseases. Androgens influence the cardiovascular physiology and pathophysiology. However, their effect on native T-type calcium currents (I(Ca,T)) remains unclear. To test the chronic effect of testosterone on the cardiac I(Ca,T), cultured neonatal rat ventricular cardiomyocytes were treated with testosterone (1 nM-10 microM) for 24-30 h. Current measurements were performed after testosterone washout to exclude any acute testosterone effects. Testosterone (100 nm) pretreatment significantly increased whole-cell I(Ca,T) density from 1.26 +/- 0.48 pA/pF (n = 8) to 5.06 +/- 1.75 pA/pF (n = 7; P < 0.05) and accelerated beating rate. This was attributed to both increased expression levels of the pore-forming subunits Ca(v)3.1 and Ca(v)3.2 and increased T-type single-channel activity. On single-channel level, the increase of the ensemble average current by testosterone vs. time-matched controls was due to an increased availability (58.1 +/- 4.2 vs. 21.5 +/- 4.0%, P < 0.01) and open probability (2.78 +/- 0.29 vs. 0.85 +/- 0.23%, P < 0.01). Cotreatment with the selective testosterone receptor antagonist flutamide (10 mum) prevented these chronic testosterone-induced effects. Conversely, acute application of testosterone (10 microM) decreased T-type single-channel activity in testosterone pretreated cells by reducing the open probability (0.78 +/- 0.13 vs. 2.91 +/- 0.38%, P < 0.01), availability (23.6 +/- 3.3 vs. 57.6 +/- 4.5%, P < 0.01), and peak current (-20 +/- 4 vs. -58 +/- 4 fA, P < 0.01). Flutamide (10 microM) did not abolish the testosterone-induced acute block of T-type calcium channels. Our results indicate that long-term testosterone treatment increases, whereas acute testosterone decreases neonatal rat T-type calcium currents. These effects seem to be mediated by a genomic chronic stimulation and a nongenomic acute inhibitory action.
在心血管系统中，T型钙通道在细胞内钙稳态和自发起搏活动中起重要作用，并参与结构性心脏病的进展。雄激素会影响心血管生理和病理生理过程。然而，它们对天然T型钙电流（I(Ca,T)）的影响仍不清楚。为了测试睾酮对心脏I(Ca,T)的慢性影响，用睾酮（1 nM - 10 microM）处理培养的新生大鼠心室心肌细胞24 - 30小时。在洗脱睾酮后进行电流测量，以排除任何急性睾酮效应。睾酮（100 nM）预处理显著增加了全细胞I(Ca,T)密度，从1.26±0.48 pA/pF（n = 8）增加到5.06±1.75 pA/pF（n = 7；P < 0.05），并加快了搏动频率。这归因于孔形成亚基Ca(v)3.1和Ca(v)3.2的表达水平增加以及T型单通道活性增加。在单通道水平上，与时间匹配的对照相比，睾酮使总体平均电流增加是由于可用性增加（58.1±4.2对21.5±4.0%，P < 0.01）和开放概率增加（2.78±0.29对0.85±0.23%，P < 0.01）。与选择性睾酮受体拮抗剂氟他胺（10 microM）共同处理可预防这些慢性睾酮诱导的效应。相反，急性应用睾酮（10 microM）通过降低开放概率（0.78±0.13对2.91±0.38%，P < 0.01）、可用性（23.6±3.3对57.6±4.5%，P < 0.01）和峰值电流（-20±4对-58±4 fA，P < 0.01），降低了睾酮预处理细胞中的T型单通道活性。氟他胺（10 microM）并未消除睾酮诱导的T型钙通道急性阻断。我们的结果表明，长期睾酮处理会增加，而急性睾酮会降低新生大鼠的T型钙电流。这些效应似乎是由基因组慢性刺激和非基因组急性抑制作用介导的。
