Stimulus-secretion coupling in platelets. Effects of drugs on secretion on adenosine 5'-triphosphate.
Stimulus-secretion coupling in platelets. Effects of drugs on secretion on adenosine 5'-triphosphate.
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血小板中的刺激-分泌耦合。
DOI：
10.1021/bi00677a033
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发表时间：
1975
期刊：
影响因子：
2.9
通讯作者：
T. Detwiler
中科院分区：
文献类型：
--
作者：
F. Friedman;T. Detwiler
通过观察药物对凝血酶或二价阳离子载体A23187诱导的血小板ATP分泌动力学的影响，研究了血小板刺激-分泌偶联的机制。实际的分泌与这些试剂中的任一种相同，因为分泌的速率常数和活化能相同，并且因为影响凝血酶诱导的分泌的最终酶非依赖性步骤的药物对离子载体诱导的分泌具有相同的作用。影响凝血酶诱导的分泌的早期步骤的药物对离子载体诱导的分泌没有影响。通过cAMP起作用的药物（PGE 1、茶碱、二丁酰-cAMP）减缓凝血酶诱导分泌机制的早期步骤，并在较高水平下完全阻断，所需的抑制剂浓度取决于凝血酶浓度。速率抑制似乎是全或无，未观察到中间速率。通过用胰蛋白酶代替凝血酶，这使得可以观察到速率决定步骤从酶依赖性血小板步骤到酶非依赖性血小板步骤的完全变化，发现这些药物仅在酶非依赖性步骤是速率决定步骤时减慢速率。这些药物对A23187诱导的分泌没有影响。得出的结论是，cAMP抑制在酶的步骤后，但在最后一步之前，通过干扰刺激分泌耦合信号的传输。细胞松弛素B（10 μ M）对微丝功能的破坏加速了凝血酶或离子载体诱导的分泌速率。微管药物秋水仙碱、长春碱和长春新碱只有在高于通常认为特异性抑制微管功能所需的浓度时才有作用。抑制前列腺素合成的药物（阿司匹林、吲哚美辛、二十碳四炔酸）、阻断ATP生成的药物（抗霉素A、脱氧葡萄糖）或其他几种先前报道的抑制血小板功能的药物对分泌没有影响。
The mechanism of stimulus-secretion coupling in platelets was investigated by observing the effects of drugs on the kinetics on ATP secretion induced by either thrombin or the divalent cation ionophore A23187. The actual secretion is the same with either of these agents, since the rate constants and activation energies of secretion are the same and since drugs that affect the final, enzyme-independent steps of thrombin-induced secretion have the same effect on ionophore-induced secretion. Drugs that affect early steps of thrombin-induced secretion have no effect on ionophore-induced secretion. Drugs that act through cAMP (PGE1, theophylline, dibutyryl-cAMP) slow an early step in the mechanism of thrombin-induced secretion and completely block at higher levels, with the required concentration of inhibitor dependent on thrombin concentration. The inhibition of rate appears to be all-or-none, with no intermediate rates observed. By replacing thrombin with trypsin, which makes it possible to observe a complete change in rate-determining step from an enzyme-dependent to an enzyme-independent platelet step, it was found that these drugs slow the rate only when the enzyme-independent step is rate determining. These drugs have no effect on A23187-induced secretion. It was concluded that cAMP inhibits at a step after the enzyme step but before the final step by interfering with transmission of the stimulus-secretion coupling signal. Disruption of microfilament function by cytochalasin B (10 muM) accelerates the rate of secretion induced by either thrombin or ionophore. The microtubule agents colchicine, vinblastine, and vincristine had effects only at concentrations above those usually considered necessary for the specific inhibition of microtubule function. Drugs that inhibit prostaglandin synthesis (aspirin, indomethacin, eicosatetraynoic acid), drugs that block ATP production (antimycin A, deoxyglucose), or several other drugs previously reported to inhibit platelet function had no effect on secretion.