Segura-Chama Pedro, López-Bistrain Patricia, Pérez-Armendáriz Elia Martha, Jiménez-Pérez Nicolás, Millán-Aldaco Diana, Hernández-Cruz Arturo
Unidad de Investigación en Medicina Experimental, 5° piso Torre de Investigación, Facultad de Medicina, Universidad Nacional Autónoma de México, Ciudad Universitaria, Mexico, Federal District, 04510, Mexico.
Hospital General de México, Mexico, Federal District, 06726, Mexico.
Pflugers Arch. 2015 Nov;467(11):2307-23. doi: 10.1007/s00424-015-1702-8. Epub 2015 Mar 21.
Adrenal chromaffin cells (CCs) from spontaneously hypertensive rats (SHRs) secrete more catecholamine (CA) upon stimulation than CCs from normotensive Wistar Kyoto rats (WKY). Unitary CA exocytosis events, both spontaneous and stimulated, were amperometrically recorded from cultured WKY and SHR CCs. Both strains display spontaneous amperometric spikes but SHR CCs produce more spikes and of higher mean amplitude. After a brief stimulation with high K(+) or caffeine which produces voltage-gated Ca(2+) influx or intracellular Ca(2+) release, respectively, more spikes and of greater mean amplitude and unitary charge were recorded in SHR CCs. Consequently, peak cumulative charge was ~2-fold higher in SHR CCs. Ryanodine (10 μM), a specific blocker of the ryanodine receptors reduced depolarization-induced peak cumulative charge by ~10 % in WKY and ~77 % in SHR CCs, suggesting, a larger contribution of Ca(2+)-induced Ca(2+) release to CA exocytosis in SHR CCs. Accordingly, Ca(2+) imaging showed larger [Ca(2+)]i signals induced both by depolarization and caffeine in SHR CCs. Distribution amplitude histograms showed that small amperometric spikes (0-50 pA) are more frequent in WKY than in SHR CCs. Conversely, medium (50-190 pA) and large (190-290 pA) spikes are more numerous in SHR than in WKY CCs. This study reveals that the enhanced CA secretion in SHR CCs results from a combination of (1) larger depolarization-induced Ca(2+) transients, due to a greater Ca(2+)-induced intracellular Ca(2+) release, (2) more exocytosis events per time unit, and (3) a greater proportion of medium and large amperometric spikes probably due to a higher mean CA content per granule. Enhanced CA release by excessive amplification by Ca(2+) induced Ca(2+) release and larger granule catecholamine content contributes to the increased CA plasma levels and vasomotor tone in SHRs.
自发性高血压大鼠（SHR）的肾上腺嗜铬细胞（CC）在受到刺激时比正常血压的Wistar Kyoto大鼠（WKY）的CC分泌更多的儿茶酚胺（CA）。通过安培法记录培养的WKY和SHR CC的自发性和受刺激的单一CA胞吐事件。两种品系均显示出自发性安培峰，但SHR CC产生更多的峰且平均幅度更高。在用高K⁺或咖啡因进行短暂刺激后，分别产生电压门控Ca²⁺内流或细胞内Ca²⁺释放，在SHR CC中记录到更多的峰、更大的平均幅度和单一电荷。因此，SHR CC中的峰值累积电荷约高2倍。Ryanodine（10 μM），一种ryanodine受体的特异性阻滞剂，使WKY中去极化诱导的峰值累积电荷降低约10%，在SHR CC中降低约77%，这表明Ca²⁺诱导的Ca²⁺释放对SHR CC中CA胞吐的贡献更大。相应地，Ca²⁺成像显示SHR CC中去极化和咖啡因诱导的[Ca²⁺]i信号更大。分布幅度直方图显示，小安培峰（0 - 50 pA）在WKY中比在SHR CC中更频繁。相反，中等（50 - 190 pA）和大（190 - 290 pA）峰在SHR中比在WKY CC中更多。这项研究表明，SHR CC中CA分泌增强是由于以下因素共同作用的结果：（1）由于更大的Ca²⁺诱导的细胞内Ca²⁺释放，去极化诱导的Ca²⁺瞬变更大；（2）每时间单位更多的胞吐事件；（3）中等和大安培峰的比例更大，这可能是由于每个颗粒的平均CA含量更高。Ca²⁺诱导的Ca²⁺释放过度放大和颗粒儿茶酚胺含量增加导致的CA释放增强导致了SHR中CA血浆水平和血管运动张力的增加。
