Williams K A, Haslam R J
Biochim Biophys Acta. 1984 Mar 14;770(2):216-23. doi: 10.1016/0005-2736(84)90133-0.
We have investigated the effects of NaCl and GTP on the inhibition of platelet adenylate cyclase by 1-O-octadecyl-2-O-acetyl-sn-glyceryl-3-phosphorylcholine (1-octadecyl-2-acetyl-G-3-PC), using particulate fractions from human and rabbit platelets that had been frozen and thawed in the presence of ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetate to prevent Ca2+-dependent proteolysis. When 10 microM GTP was present, 100 mM NaCl stimulated the activity of the rabbit enzyme 5.6-fold and that of the human enzyme 2.2-fold. Under these conditions, maximum inhibitions of 90% and 64% were obtained on addition of 100 nM 1-octadecyl-2-acetyl-G-3-PC to rabbit and human preparations, respectively. These inhibitions resulted partly from an NaCl-independent inhibition of basal enzyme activity and partly from reversal of the stimulatory effect of NaCl. The relative abilities of the chlorides of different monovalent cations to enhance inhibition of rabbit platelet adenylate cyclase were: NaCl greater than LiCl greater than KCl greater than choline chloride. NaCl also increased the concentrations of 1-octadecyl-2-acetyl-G-3-PC required for half-maximal inhibition of adenylate cyclase but this action of NaCl did not correlate with its stimulatory effect on enzyme activity. After particulate fractions from platelets of either species were washed, 10 microM GTP inhibited basal adenylate cyclase activity in the absence of NaCl but stimulated the enzyme in the presence of NaCl. Inhibition of adenylate cyclase by 1-octadecyl-2-acetyl-G-3-PC was then either enhanced by GTP (rabbit material) or completely dependent on added GTP (human material). Stimulation of the activity of the washed human preparations by NaCl required GTP, but concentrations lower than required for potentiation of the inhibitory effect of 1-octadecyl-2-acetyl-G-3-PC by NaCl were effective.
我们使用来自人和兔血小板的微粒体部分，研究了NaCl和GTP对1 - O - 十八烷基 - 2 - O - 乙酰基 - sn - 甘油 - 3 - 磷酸胆碱（1 - 十八烷基 - 2 - 乙酰基 - G - 3 - PC）抑制血小板腺苷酸环化酶的影响。这些微粒体部分是在乙二醇双（β - 氨基乙醚） - N，N，N'，N' - 四乙酸存在下冷冻和解冻的，以防止Ca2 +依赖性蛋白水解。当存在10μM GTP时，100 mM NaCl刺激兔酶的活性达5.6倍，刺激人酶的活性达2.2倍。在这些条件下，向兔和人制剂中分别添加100 nM 1 - 十八烷基 - 2 - 乙酰基 - G - 3 - PC时，最大抑制率分别为90％和64％。这些抑制部分源于对基础酶活性的NaCl非依赖性抑制，部分源于NaCl刺激作用的逆转。不同单价阳离子的氯化物增强兔血小板腺苷酸环化酶抑制的相对能力为：NaCl＞LiCl＞KCl＞氯化胆碱。NaCl还增加了腺苷酸环化酶半最大抑制所需的1 - 十八烷基 - 2 - 乙酰基 - G - 3 - PC的浓度，但NaCl的这种作用与其对酶活性的刺激作用无关。在洗涤任一物种血小板的微粒体部分后，10μM GTP在无NaCl时抑制基础腺苷酸环化酶活性，但在有NaCl时刺激该酶。然后，1 - 十八烷基 - 2 - 乙酰基 - G - 3 - PC对腺苷酸环化酶的抑制作用在兔材料中被GTP增强，在人材料中则完全依赖于添加的GTP。NaCl对洗涤后的人制剂活性的刺激需要GTP，但低于NaCl增强1 - 十八烷基 - 2 - 乙酰基 - G - 3 - PC抑制作用所需浓度的GTP就有效。
