Division of Drug Research/Pharmacology, Department of Medical and Health Sciences, Linköping University , SE-581 85 Linköping , Sweden.
Platelets. 2013;24(2):129-35. doi: 10.3109/09537104.2012.672780. Epub 2012 Apr 3.
Adrenaline is a platelet activator having a resting plasma concentration of <1 nmol/l that increases to a few nmol/l during stress. However, most in vitro assays only detect effects of adrenaline in micromolar concentrations. This makes it difficult to estimate the relevance of in vitro data for the in vivo situation. The aim of this study was to investigate experimental conditions in vitro that could detect platelet effects of adrenaline in nanomolar concentrations. Platelet adhesion to albumin and collagen was evaluated with a static platelet adhesion assay. Our results show that 10 nmol/l adrenaline induced platelet adhesion to albumin in platelet-rich plasma (PRP) prepared at 140 × g, while 100 nmol/l was necessary in order to increase adhesion of platelets prepared at 220 × g. The mean platelet volume was increased after preparation at 140 × g, suggesting that large reactive platelets contributed to the increased adrenaline sensitivity. At optimal Mg(2+)-concentration, adhesion to collagen was increased by 10 nmol/l adrenaline irrespective of centrifugal force applied during PRP preparation. More specifically, we defined two populations where adhesion to collagen was increased by 10 nmol/l adrenaline either upon centrifugation at 140 × g but not 220 × g or vice versa. In some experiments, platelet adhesion to collagen was induced by 3 nmol/l adrenaline, which corresponds to concentrations achieved during stress in vivo. In summary, the static adhesion assay is able to detect platelet activating effects of adrenaline very close to physiological concentrations. This is rare for in vitro assays and motivates further research about adrenergic signalling in platelets.
肾上腺素是一种血小板激活剂，静息状态下的血浆浓度<1 nmol/L，在应激状态下可增加到几个 nmol/L。然而，大多数体外检测方法仅能检测到几微摩尔浓度的肾上腺素的作用。这使得很难评估体外数据与体内情况的相关性。本研究旨在探讨体外实验条件，以检测纳摩尔浓度肾上腺素对血小板的影响。采用静态血小板黏附试验评估血小板对白蛋白和胶原的黏附作用。我们的结果表明，10 nmol/L 的肾上腺素可诱导富含血小板的血浆（PRP）中血小板黏附于白蛋白，而在 220×g 制备 PRP 时，则需要 100 nmol/L 才能增加血小板的黏附。在 140×g 制备时，血小板平均体积增加，表明大反应性血小板有助于增加肾上腺素的敏感性。在最佳 Mg2+浓度下，10 nmol/L 的肾上腺素增加了胶原黏附，而与 PRP 制备过程中的离心力无关。更具体地说，我们定义了两个群体，其中 10 nmol/L 的肾上腺素要么在 140×g 离心但不在 220×g 离心时增加胶原黏附，要么反之亦然。在某些实验中，3 nmol/L 的肾上腺素可诱导血小板黏附于胶原，这与体内应激时的浓度相对应。总之，静态黏附试验能够检测到非常接近生理浓度的肾上腺素激活血小板的作用。这在体外检测中很少见，促使我们进一步研究肾上腺素在血小板中的信号传递。
