Savage B, McFadden P R, Hanson S R, Harker L A
Blood. 1986 Aug;68(2):386-93.
The relationship between platelet density and platelet age has been studied using continuous linear Percoll density gradients and 111In-labeling of autologous platelets in baboons. To investigate changes in platelet density during senescence in the circulation, baboons were infused with 111In-labeled autologous platelets, and blood was collected at one hour postinfusion and twice daily thereafter for six days. Platelets were isolated from these samples in high yield (greater than 95%) and separated in continuous linear Percoll density gradients following density equilibrium centrifugation. Although at one hour postinfusion the density distribution of radiolabeled platelets coincided closely with the distribution of the total platelet population, a detectable symmetrical shift toward higher densities was observed after five days. The relative specific radioactivity (RSR) of high-density platelets (1.064 to 1.067 g/mL) decreased at a slower rate than that of the total platelet population (platelets of all densities), whereas the RSR of low-density platelets (1.053 to 1.056 g/mL) showed a more immediate and rapid decrease. These results give rise to one of two interpretations: (1) low-density platelets have a shorter survival time than more dense platelets and are therefore cleared from the circulation at a faster rate, or (2) platelets of all densities increase in density upon aging in the circulation. To determine the explanation for changing RSR of different density fractions we studied the in vivo disappearance characteristics of low- and high-density 111In-labeled platelets. There were no significant differences between the mean survival times of low-density platelets (5.0 +/- 0.49 days, +/- 1 SD, n = 6), high-density platelets (4.9 +/- 0.56 days, n = 6), or control platelets representing platelets of all densities (4.9 +/- 0.38 days, n = 6). Although a slight increase in the density of all platelets during platelet senescence is indicated by these studies, we conclude that platelet density heterogeneity is not primarily a consequence of age-related changes in platelet density.
利用连续线性 Percoll 密度梯度和狒狒自体血小板的 111In 标记，研究了血小板密度与血小板年龄之间的关系。为了研究循环中衰老过程中血小板密度的变化，给狒狒输注 111In 标记的自体血小板，输注后 1 小时采集血液，此后每天采集两次，共采集六天。从这些样本中以高产率（大于 95%）分离出血小板，并在密度平衡离心后在连续线性 Percoll 密度梯度中进行分离。尽管在输注后 1 小时，放射性标记血小板的密度分布与总血小板群体的分布密切吻合，但五天后观察到向更高密度的可检测到的对称偏移。高密度血小板（1.064 至 1.067 g/mL）的相对比放射性（RSR）下降速度比总血小板群体（所有密度的血小板）慢，而低密度血小板（1.053 至 1.056 g/mL）的 RSR 显示出更直接和快速的下降。这些结果产生了两种解释之一：（1）低密度血小板的存活时间比高密度血小板短，因此从循环中清除的速度更快，或者（2）所有密度的血小板在循环中衰老时密度都会增加。为了确定不同密度组分 RSR 变化的解释，我们研究了低密度和高密度 111In 标记血小板的体内消失特征。低密度血小板（5.0±0.49 天，±1 SD，n = 6）、高密度血小板（4.9±0.56 天，n = 6）或代表所有密度血小板的对照血小板（4.9±0.38 天，n = 6）的平均存活时间之间没有显著差异。尽管这些研究表明血小板衰老过程中所有血小板的密度略有增加，但我们得出结论，血小板密度异质性并非主要是血小板密度与年龄相关变化的结果。
