Wang C N, Chen J C, Shiao M S, Wang C T
Institute of Life Science, National Tsing Hua University, Hsinchu, Taiwan, Republic of China.
Biochem J. 1991 Jul 1;277 ( Pt 1)(Pt 1):189-97. doi: 10.1042/bj2770189.
Human gel-filtered platelets aggregate at greater than 20 microM-ganodermic acid S [lanosta-7,9(11),24-triene-3 beta, 15 alpha-diacetoxy-26-oic acid] [Wang, Chen, Shiao & Wang (1989) Biochim. Biophys. Acta 986, 151-160]. This study showed that platelets at less than 20 microM-ganodermic acid S displayed both concentration- and time-dependent inhibition of function, in which the agent potency in response to inducers was ADP-fibrinogen greater than collagen greater than thrombin. The agent caused a biphasic time-dependent effect on platelet phosphoinositide metabolism. The first phase involved the decrease in the pool size of phosphoinositide by 10-20%. The second phase, in which both the resynthesis of phosphatidylinositol 4,5-bisphosphate (PIP2) and the decrease of [32P]phosphatidic acid occurred, took place after 30 min. Scanning electron microscopy also revealed a time-dependent morphological change in platelets in the presence of the agent. The cells initially became spiculate discs, then swelled to a 'potato-like' morphology at 60 min. Further studies on the time-dependent inhibition of thrombin response revealed that: (1) the percentage inhibition of cell aggregation was comparable with that occurring with an increase of cytosolic free Ca2+ concentration [( Ca2+]i) or the phosphorylation of marker proteins; (2) [32P]Pi-labelled platelets showed the time-dependent inhibition of thrombin-stimulated PIP2 resynthesis as indicated by first-2-min time-course studies of phosphoinositide interconversion; (3) scanning electron microscopy revealed that the aged platelet population showed an increase in the percentage of non-responding cells on prolonged incubation. The results, taken together, enabled one to discuss a possible mechanism for the time-dependent inhibition by ganodermic acid S of platelet response to thrombin.
人凝胶过滤血小板在大于20微摩尔的灵芝酸S [羊毛甾-7,9(11),24-三烯-3β,15α-二乙酰氧基-26-酸]作用下会发生聚集[王、陈、萧和王(1989年)《生物化学与生物物理学报》986, 151 - 160]。本研究表明，低于20微摩尔灵芝酸S时，血小板功能呈现浓度和时间依赖性抑制，其中该药物对诱导剂的效力为ADP - 纤维蛋白原大于胶原大于凝血酶。该药物对血小板磷酸肌醇代谢产生双相时间依赖性效应。第一阶段涉及磷酸肌醇池大小减少10 - 20%。第二阶段，磷脂酰肌醇4,5 - 二磷酸（PIP2）的再合成以及[32P]磷脂酸的减少均发生在30分钟后。扫描电子显微镜还揭示了在该药物存在下血小板随时间的形态变化。细胞最初变成有刺的圆盘状，然后在60分钟时膨胀成“土豆样”形态。对凝血酶反应的时间依赖性抑制的进一步研究表明：(1)细胞聚集的抑制百分比与细胞溶质游离Ca2 +浓度[(Ca2 +]i)增加或标记蛋白磷酸化时的情况相当；(2)[32P]Pi标记的血小板显示出凝血酶刺激的PIP2再合成的时间依赖性抑制，如磷酸肌醇相互转化的前2分钟时间进程研究所表明的；(3)扫描电子显微镜显示，随着孵育时间延长，老化血小板群体中无反应细胞的百分比增加。综合这些结果，人们能够讨论灵芝酸S对血小板对凝血酶反应的时间依赖性抑制的可能机制。
