Er Fikret, Michels Guido, Brandt Mathias C, Khan Ismail, Haase Hannelore, Eicks Michael, Lindner Michael, Hoppe Uta C
Department of Internal Medicine III, University of Cologne, Kerpener Str. 62, 50937 Cologne, Germany.
Cell Calcium. 2007 May;41(5):467-77. doi: 10.1016/j.ceca.2006.09.003. Epub 2006 Nov 7.
While androgens generally have been associated with an increased cardiovascular risk, recent studies indicate potential beneficial acute effects of testosterone. However, detailed evaluation of chronic and acute actions of testosterone on the function of cardiac I(Ca,L) and intracellular Ca2+ handling is limited. To clarify this situation we performed whole-cell and single-channel analysis of I(Ca,L), recordings of Ca2+ sparks, measurements of contractility and quantitative real-time RT-PCR in rat cardiomyocytes following testosterone pretreatment and acute testosterone application. Pretreatment with testosterone 100 nM for 24-30 h increased whole-cell I(Ca,L) from 3.8+/-0.8 pA/pF (n=10) to 10.1+/-0.31 pA/pF (n=9) at +10 mV (p<0.001). Increase of I(Ca,L) density was caused by both, increased expression levels of the alpha 1C subunit of L-type calcium channel and a pronounced increment of the single-channel activity (availability 81.8+/-3.15% versus 37.1+/-7.01%; open probability 12.8+/-3.09% versus 1.0+/-0.62%, p<0.01). Moreover, testosterone pretreatment significantly increased the frequency of Ca2+ sparks and improved myocytes contractility without altering SR Ca2+ load. All chronic effects could be inhibited by flutamide. In contrast acute testosterone administration significantly reduced I(Ca,L) density. Indeed, on the single-channel level acute testosterone application completely reversed the chronic testosterone-mediated effects, and antagonized the chronic testosterone effects on Ca2+ spark frequency, which was unaffected by flutamide. Thus, testosterone pretreatment activates I(Ca,L) via nuclear receptor-mediated pathways, while testosterone acutely blocks I(Ca,L) in a direct manner. Thus, testosterone chronically affects the basal level of intracellular Ca2+ handling, which in addition rapidly may be modulated by acute changes of hormone levels.
虽然雄激素通常与心血管风险增加有关，但最近的研究表明睾酮具有潜在的有益急性作用。然而，关于睾酮对心脏L型钙电流（I(Ca,L)）功能和细胞内钙处理的慢性和急性作用的详细评估有限。为了阐明这种情况，我们在睾酮预处理和急性给予睾酮后，对大鼠心肌细胞进行了I(Ca,L)的全细胞和单通道分析、钙火花记录、收缩性测量以及定量实时逆转录聚合酶链反应（RT-PCR）。用100 nM睾酮预处理24 - 30小时后，在+10 mV时全细胞I(Ca,L)从3.8±0.8 pA/pF（n = 10）增加到10.1±0.31 pA/pF（n = 9）（p < 0.001）。I(Ca,L)密度的增加是由于L型钙通道α1C亚基的表达水平增加以及单通道活性的显著增加（可用性81.8±3.15%对37.1±7.01%；开放概率12.8±3.09%对1.0±0.62%，p < 0.01）。此外，睾酮预处理显著增加了钙火花的频率并改善了心肌细胞的收缩性，而不改变肌浆网钙负荷。所有慢性作用均可被氟他胺抑制。相比之下，急性给予睾酮显著降低了I(Ca,L)密度。实际上，在单通道水平上，急性给予睾酮完全逆转了慢性睾酮介导的作用，并拮抗了慢性睾酮对钙火花频率的影响，而氟他胺对此无影响。因此，睾酮预处理通过核受体介导的途径激活I(Ca,L)，而睾酮急性则直接阻断I(Ca,L)。因此，睾酮长期影响细胞内钙处理的基础水平，此外，激素水平的急性变化可能会迅速对其进行调节。
