Touyz R M, Schiffrin E L
Clinical Research Institute of Montreal, University of Montreal, Quebec, Canada.
Hypertension. 1993 Dec;22(6):853-62. doi: 10.1161/01.hyp.22.6.853.
The aims of this study were to determine the relations between platelet free calcium concentrations ([Ca2+]i), intracellular pH (pHi), and aggregation and to assess the effects of angiotensin II (Ang II) and endothelin-1 on these platelet parameters in normotensive subjects and hypertensive patients. Seventeen normotensive subjects, 25 untreated hypertensive patients, and 34 treated hypertensive patients were studied. Platelet cytosolic free [Ca2+]i and pHi were measured spectrofluorometrically using specific fluorescent probes (fura 2-AM and BCECF-AM, respectively) in unstimulated and Ang II- and endothelin-1-stimulated platelets. Aggregation was measured by a turbidometric technique. Basal [Ca2+]i (141 +/- 11 nmol/L) and pH (7.16 +/- 0.01) were higher (P < .05) in the untreated hypertensive group compared with the normotensive (118 +/- 9 nmol/L, 7.11 +/- 0.01, respectively) and treated hypertensive (121 +/- 11 nmol/L, 7.12 +/- 0.01, respectively) groups. In the combined normotensive and hypertensive groups, there were significant correlations between [Ca2+]i and mean arterial pressure (r = .75, P < .01), pHi and mean arterial pressure (r = .72, P < .01), [Ca2+]i and pHi (r = .71, P < .01), [Ca2+]i and aggregation (r = .69, P < .02), and pHi and aggregation (r = .56, P < .05). Ang II stimulation significantly increased [Ca2+]i and pHi in the untreated hypertensive and normotensive groups. The net change in [Ca2+]i induced by Ang II was significantly higher (P < .05) in the untreated hypertensive group compared with the other groups (67 +/- 6 nmol/L for the untreated hypertensive group versus 54 +/- 5 and 29 +/- 8 nmol/L for the normotensive and treated hypertensive groups, respectively). In the presence of Ang II, thrombin-induced aggregatory responses were increased in all three groups, but the maximal response was significantly higher in the untreated hypertensive group compared with the other groups (P < .05). Endothelin-1 increased pHi through endothelin A-receptors (effect blocked by the specific antagonist BQ-123) but had no significant effect on [Ca2+]i or aggregation. However, endothelin-1 blunted thrombin-induced platelet aggregation in normotensive subjects but not in hypertensive patients. In conclusion, increased Ang II-stimulated [Ca2+]i and pHi in platelets of essential hypertensive patients may be associated with increased aggregatory responses. The stimulatory effect of endothelin-1 on pHi but not on [Ca2+]i or aggregation suggests that in platelets endothelin-induced signaling pathways other than phospholipase C may be involved.(ABSTRACT TRUNCATED AT 400 WORDS)
本研究的目的是确定血小板游离钙浓度（[Ca2+]i）、细胞内pH值（pHi）与聚集之间的关系，并评估血管紧张素II（Ang II）和内皮素-1对正常血压受试者和高血压患者这些血小板参数的影响。研究了17名正常血压受试者、25名未经治疗的高血压患者和34名接受治疗的高血压患者。使用特定的荧光探针（分别为fura 2-AM和BCECF-AM）通过分光荧光法测量未刺激的以及Ang II和内皮素-1刺激的血小板中的血小板胞质游离[Ca2+]i和pHi。通过比浊法测量聚集。与正常血压组（分别为118±9 nmol/L，7.11±0.01）和接受治疗的高血压组（分别为121±11 nmol/L，7.12±0.01）相比，未经治疗的高血压组的基础[Ca2+]i（141±11 nmol/L）和pH值（7.16±0.01）更高（P<0.05）。在正常血压和高血压合并组中，[Ca2+]i与平均动脉压（r = 0.75，P<0.01）、pHi与平均动脉压（r = 0.72，P<0.01）、[Ca2+]i与pHi（r = 0.71，P<0.01）、[Ca2+]i与聚集（r = 0.69，P<0.02）以及pHi与聚集（r = 0.56，P<0.05）之间存在显著相关性。Ang II刺激显著增加了未经治疗的高血压组和正常血压组中的[Ca2+]i和pHi。与其他组相比，Ang II诱导的[Ca2+]i净变化在未经治疗的高血压组中显著更高（P<0.05）（未经治疗的高血压组为67±6 nmol/L，而正常血压组和接受治疗的高血压组分别为54±5和29±8 nmol/L）。在存在Ang II的情况下，所有三组中凝血酶诱导的聚集反应均增加，但未经治疗的高血压组的最大反应与其他组相比显著更高（P<0.05）。内皮素-1通过内皮素A受体增加pHi（该效应被特异性拮抗剂BQ-123阻断），但对[Ca2+]i或聚集无显著影响。然而，内皮素-1减弱了正常血压受试者中凝血酶诱导的血小板聚集，但在高血压患者中则不然。总之，原发性高血压患者血小板中Ang II刺激的[Ca2+]i和pHi增加可能与聚集反应增加有关。内皮素-1对pHi有刺激作用，但对[Ca2+]i或聚集无作用，这表明在血小板中，除磷脂酶C外，内皮素诱导的信号通路可能也参与其中。（摘要截短至400字）
