Sandmann J, Leissner J, Lindmar R, Löffelholz K
Department of Pharmacology, University of Mainz, F.R.G.
Eur J Pharmacol. 1990 Mar 13;188(2-3):89-95. doi: 10.1016/0922-4106(90)90043-w.
The efflux of choline was determined in rat striatal slices, incubated chicken atria and perfused chicken hearts. 4 beta-Phorbol-12 beta,13 alpha-dibutyrate (PDB) and 4 beta-phorbol-12 beta-myristate, 13 alpha-acetate (PMA) were used to stimulate protein kinase C. The other phorbol esters, 4 beta-phorbol-13 alpha-acetate (PAc) and 4 alpha-phorbol-12 beta,13 alpha-didecanoate (4 alpha PDD), known to be inactive, were tested to evaluate the specificity of the responses. PDB markedly enhanced the efflux of choline in all of the three preparations. The PDB-evoked efflux of choline in incubated chicken atria was equal to the net production of choline and, therefore, was not caused by translocation of intracellular free choline. After inhibition of the cholinesterase activity, PDB linearly increased the efflux of choline in rat striatal slices, but failed to alter the spontaneous efflux of acetylcholine. Thus acetylcholine did not serve as the source of the PDB-evoked efflux of choline. PMA was as effective as PDB, whereas PAc and 4 alpha PDD failed to alter the choline efflux in the perfused heart. Both infusion of a Ca2(+)-free EGTA-containing Tyrode solution and mepacrine reduced the spontaneous efflux of choline by about 40% and blocked the PDB-evoked efflux of choline. In contrast, a Ca2(+)-free solution without EGTA failed to alter the spontaneous and the PDB-evoked choline efflux. It is concluded that phorbol esters stimulate the hydrolysis of choline-containing phospholipids in heart and brain via activation of protein kinase C.
在大鼠纹状体切片、孵育的鸡心房和灌流的鸡心脏中测定胆碱的流出。使用4β-佛波醇-12β,13α-二丁酸酯（PDB）和4β-佛波醇-12β-肉豆蔻酸酯-13α-乙酸酯（PMA）刺激蛋白激酶C。还测试了已知无活性的其他佛波酯，4β-佛波醇-13α-乙酸酯（PAc）和4α-佛波醇-12β,13α-十二烷酸酯（4αPDD），以评估反应的特异性。PDB显著增强了所有三种制剂中胆碱的流出。在孵育的鸡心房中，PDB引起的胆碱流出量与胆碱的净生成量相等，因此不是由细胞内游离胆碱的转运引起的。抑制胆碱酯酶活性后，PDB使大鼠纹状体切片中胆碱的流出量呈线性增加，但未能改变乙酰胆碱的自发流出。因此，乙酰胆碱不是PDB引起的胆碱流出的来源。PMA与PDB一样有效，而PAc和4αPDD未能改变灌流心脏中胆碱的流出。输注不含Ca2+的含EGTA的Tyrode溶液和甲氯芬酯均可使胆碱的自发流出减少约40%，并阻断PDB引起的胆碱流出。相比之下，不含EGTA的无Ca2+溶液未能改变自发的和PDB引起的胆碱流出。结论是佛波酯通过激活蛋白激酶C刺激心脏和大脑中含胆碱磷脂的水解。
