Ederveen A G, van Emst-de Vries S E, De Pont J J, Willems P H
Department of Biochemistry, University of Nijmegen, The Netherlands.
Eur J Biochem. 1990 Mar 10;188(2):333-8. doi: 10.1111/j.1432-1033.1990.tb15408.x.
The putative inhibitor of diacylglycerol kinase activity, 6-(2-[(4-fluorophenyl)phenylmethylene]-1-piperidinyl)-ethyl-7-meth yl-5H- thiazolo[3,2-a]pyrimidin-5-one (R59022), markedly potentiated cholecystokinin-C-terminal-octapeptide(CCK-8-)stimulated enzyme secretion from isolated rabbit pancreatic acini. Maximal potentiation occurred when acini were stimulated in the presence of 5-10 microM R59022. Potentiation depended both on the concentration of R59022 and CCK-8. No potentiation was observed when acini were half-maximally stimulated, whereas the secretory response to maximal and supramaximal concentrations of secretagogue was increased by 50-60%. R59022 alone had no effect on basal enzyme secretion and the drug did not potentiate the secretory response to the Ca2+ ionophore A23187 or to the phorbol ester, 12-O-tetradecanoylphorbol 13-acetate. Moreover, no increase in basal secretion was observed when acini were incubated in the presence of both R59022 and forskolin. These observations strongly suggest that receptor-mediated activation of the inositol phospholipid pathway is required for R59022-induced potentiation. R59022 inhibited the CCK-8-stimulated incorporation of 32Pi into phosphatidic acid dose dependently, without affecting the CCK-8-stimulated hydrolysis of 32P-labelled phosphatidylinositol 4,5-bisphosphate. This is consistent with an inhibitory effect of R59022 on acinar cell diacylglycerol kinase activity. The potentiating effect of R59022 was mimicked by 12-O-tetradecanoylphorbol 13-acetate added simultaneously with CCK-8. Therefore, it is concluded that in the presence of 5-10 microM R59022 the receptor-mediated increase in acinar cell diacylglycerol content is enhanced leading to enhanced activation of protein kinase C and to potentiation of the secretory response. The fact that the secretory response to maximal and supramaximal concentrations of CCK-8 is potentiated by R59022 suggests that at these concentrations of secretagogue the diacylglycerol/protein kinase C branch of the signal-transduction route is rate-limiting.
二酰基甘油激酶活性的假定抑制剂6-(2-[(4-氟苯基)苯基亚甲基]-1-哌啶基)-乙基-7-甲基-5H-噻唑并[3,2-a]嘧啶-5-酮（R59022）可显著增强胆囊收缩素C末端八肽（CCK-8）刺激的离体兔胰腺腺泡的酶分泌。当腺泡在5-10微摩尔R59022存在下受到刺激时，出现最大增强作用。增强作用既取决于R59022的浓度，也取决于CCK-8的浓度。当腺泡受到半最大刺激时未观察到增强作用，而对最大和超最大浓度促分泌剂的分泌反应增加了50-60%。单独的R59022对基础酶分泌无影响，且该药物不会增强对Ca2+离子载体A23187或佛波酯12-O-十四烷酰佛波醇13-乙酸酯的分泌反应。此外，当腺泡在R59022和福斯高林同时存在的情况下孵育时，未观察到基础分泌增加。这些观察结果强烈表明，R59022诱导的增强作用需要受体介导的肌醇磷脂途径的激活。R59022剂量依赖性地抑制CCK-8刺激的32Pi掺入磷脂酸，而不影响CCK-8刺激的32P标记的磷脂酰肌醇4,5-二磷酸的水解。这与R59022对腺泡细胞二酰基甘油激酶活性的抑制作用一致。R59022的增强作用可被与CCK-8同时添加的12-O-十四烷酰佛波醇13-乙酸酯模拟。因此，可以得出结论，在5-10微摩尔R59022存在下，受体介导的腺泡细胞二酰基甘油含量增加得到增强，导致蛋白激酶C的激活增强以及分泌反应增强。R59022增强对最大和超最大浓度CCK-8的分泌反应这一事实表明，在这些促分泌剂浓度下，信号转导途径的二酰基甘油/蛋白激酶C分支是限速的。
