Acetylcholine increases the breakdown of triphosphoinositide of rabbit iris muscle prelabelled with [32P] phosphate.
Acetylcholine increases the breakdown of triphosphoinositide of rabbit iris muscle prelabelled with [32P] phosphate.
复制标题
乙酰胆碱增加用[32P]磷酸盐预标记的兔虹膜肌肉中三磷酸肌醇的分解。
DOI：
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发表时间：
1977
影响因子：
4.1
通讯作者：
John N. HAWTHORNEt
中科院分区：
文献类型：
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作者：
A. Abdel‐Latif;R. A. Akhtar;John N. HAWTHORNEt
1.兔成对虹膜平滑肌在含葡萄糖、肌醇、胞苷和[~(32)P]磷酸的等渗盐介质中37℃孵育30分钟。2.其中一组在37℃下，在含有10 mM-2-脱氧葡萄糖的未标记的培养液中孵育10分钟，另一对在乙酰胆碱+eserine(各0.05 mM)的存在下孵育。在孵育液中加入2-脱氧葡萄糖，以减少三磷酸腺苷和二磷酸肌醇的生物合成，使标记的三磷酸腺苷的量减少了71%，并抑制了~(32)P从三磷酸肌醇进一步掺入到三磷酸肌醇中，减少了近30%。3.在~(32)P标记的虹膜肌肉中，乙酰胆碱(0.05 mM)显著增加~(32)P从三磷肌醇的损失(即‘三磷肌醇效应’)。这一效应是通过化学和放射化学方法测量的。在孵育液中用肌醇[~3H]肌醇取代~(32)PI也能观察到这一现象。4.三磷酸肌醇的作用可被阿托品阻断，但不能被D-管胡萝卜碱阻断。此外，发现毒碱类激动剂而不是尼古丁类激动剂会引起这种效应。5.乙酰胆碱使~(32)P掺入三磷酸肌醇的量减少了28%，可能是通过刺激其分解。三磷酸肌醇的这种减少可被阿托品阻断，但不能被D-管库拉林阻断。6.三磷酸肌醇效应伴随着磷脂酰肌醇和磷脂酸的~(32)P标记显著增加，但组织浓度没有显著增加。讨论了乙酰胆碱引起的~(32)P标记丢失与磷脂酰肌醇和磷脂酸标记增加之间的可能关系。7.证实了虹膜平滑肌中可能被神经递质刺激的三磷酸肌醇磷酸单酯酶的存在，在我们的匀浆和检测方法下，其活性的80%以上定位于颗粒部分。
1. Paired iris smooth muscles from rabbits were incubated for 30 min at 37 degrees C in an iso-osmotic salt medium containg glucose, inositol, cytidine and [32P]phosphate. 2. One of the pair was then incubated at 37 degrees C for 10 min in unlabelled medium containing 10mM-2-deoxyglucose and the other was incubated in the presence of acetylcholine plus eserine (0.05mM each). 2-Deoxyglucose, which was included in the incubation medium to minimize the biosynthesis of triphosphoinositide from ATP and diphosphoinositide, decreased the amount of labelled ATP by 71% and inhibited further 32P incorporation from ATP into triphosphoinositide by almost 30%. 3. Acetylcholine (0.05mM) increased significantly the loss of 32P from triphosphoinositide (the 'triphosphoinositide effect') in 32P-labelled iris muscle. This effect was measured both chemically and radiochemically. It was also observed when 32Pi was replaced by myo-[3H]inositol in the incubation medium. 4. The triphosphoinositide effect was blocked by atropine but not by D-tubocurarine. Further, muscarinic but not nicotinic agonists were found to provoke this effect. 5. Acetylcholine decreased by 28% the 32P incorporation into triphosphoinositide, presumably by stimulating its breakdown. This decrement in triphosphoinositide was blocked by atropine, but not by D-tubocurarine. 6. The triphosphoinositide effect was accompanied by a significant increase in 32P labelling, but not tissue concentration, of phosphatidylinositol and phosphatidic acid. The possible relationship between the loss of 32P label from triphosphoinositide in response to acetylcholine and the concomitant increase in that of phosphatidylinositol and phosphatidic acid is discussed. 7. The presence of triphosphoinositide phosphomonoesterase, the enzyme that might be stimulated in the iris smooth muscle by the neurotransmitter, was demonstrated, and, under our methods of homogenization and assay, more than 80% of its activity was localized in the particulate fraction.