ARACHIDONIC-ACID AND DIACYLGLYCEROL RELEASE ASSOCIATED WITH INHIBITION OF MYOSIN LIGHT-CHAIN DEPHOSPHORYLATION IN RABBIT SMOOTH-MUSCLE
ARACHIDONIC-ACID AND DIACYLGLYCEROL RELEASE ASSOCIATED WITH INHIBITION OF MYOSIN LIGHT-CHAIN DEPHOSPHORYLATION IN RABBIT SMOOTH-MUSCLE
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DOI：
10.1113/jphysiol.1995.sp020795
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发表时间：
1995-07-01
影响因子：
5.5
通讯作者：
SOMLYO, AP
中科院分区：
文献类型：
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作者：
GONG, MC;KINTER, MT;SOMLYO, AP
1.外源性花生四烯酸（AB）抑制使平滑肌肌球蛋白去磷酸化的蛋白磷酸酶，从而使收缩反应对Ca 2+敏感;它还抑制平滑肌中的电压门控Ca 2+通道。本研究的目的是确定内源性AA是否增加激动剂的方式与其作为信使调节肌球蛋白磷酸酶和Ca 2+通道的作用一致。在用α（1）-肾上腺素能激动剂苯肾上腺素（PE）（完整和透化平滑肌）或鸟苷-5 '-O-（3-硫代三磷酸）（GTP γ S;透化平滑肌，其中[Ca 2 +]保持恒定）刺激的[H-3] AA标记的完整和透化（用葡萄球菌α毒素）兔股动脉中测量AA和二酰基甘油（DAG）。采用气相色谱-质谱联用仪（GC-MS）测定花生四烯酸的质量.在完整平滑肌中，PE显著增加AA和DAG水平，分别为基线值的210和145%。另一种Ca 2+增敏剂血栓素类似物U46619引起兔肺动脉AA和DAG水平的类似增加。在恒定的[Ca 2 +]（pCa 6.5）GTP γ S诱导的AA和DAG释放前力的发展和GTP γ S（50 μ M，10分钟）增加AA质量61-88 μ M。佛波醇-12，13-二丁酸酯（PDBu）是另一种钙离子增敏剂，在pCa 6.5时也增加了透化平滑肌中AA和DAG的水平，而无活性的类似物4 α-佛波醇没有钙离子增敏作用，也没有增加AA和DAG的水平。在几乎不存在Ca 2+（pCa > 8）的情况下，GTP γ S也使AA和DAG水平分别增加3.5倍和1.6倍。游离Ca 2+本身对AA和DAG释放的影响在生理范围内（pCa 7.0至pCa 6.0）是适度的，但pCa 4.5导致AA和DAG水平与pCa 8时的水平相比增加约3至4倍。在保持恒定[Ca 2 +]（pCa 6.0）的透化回肠平滑肌中，卡巴胆碱也在其应用的1分钟内将AA显著增加至其原始值的1.75倍。我们的结果是一致的，虽然没有证明，AA和DAO的作用作为第二和/或共同信使（S）在平滑肌中，而AA和DAG水平的增加诱导PDBu提高的可能性，他们有助于佛波酯的一些细胞效应。
1. Exogenous arachidonic acid (AB) inhibits the protein phosphatase that dephosphorylates smooth muscle myosin, thus sensitizing the contractile response to Ca2+; it also inhibits voltage-gated Ca2+ channels in smooth muscle. The purpose of the present study was to determine whether endogenous AA is increased by agonists in a manner consistent with its role as a messenger regulating myosin phosphatase and Ca2+ channels. Both AA and diacylglycerol (DAG) were measured in [H-3]AA-labelled intact and permeabilized (with staphylococcal alpha-toxin) rabbit femoral arteries stimulated with the alpha(1)-adrenergic agonist phenylephrine (PE) (intact and permeabilized smooth muscles) or by guanosine-5'-O-(3-thiotriphosphate (GTP gamma S; permeabilized smooth muscles in which the [Ca2+] was maintained constant). Arachidonic acid mass was determined with gas chromatography and mass spectrometry (GC-MS).2. In intact smooth muscle, PE increased both AA and DAG; levels significantly, to 210 and 145% of baseline values, respectively. Another Ca2+-sensitizing agent, the thromboxane analogue U46619, caused a similar increase in AA and DAG; levels in rabbit pulmonary artery.3. In permeabilized smooth muscle at constant [Ca2+] (pCa 6.5) GTP gamma S-induced AA and DAG release preceded force development and GTP gamma S (50 mu M, 10 min) increased AA mass to 61-88 mu M.4. Phorbol-12,13-dibutyrate (PDBu), another Ca2+-sensitizing agent, also increased both AA and DAG levels in permeabilized smooth muscle at pCa 6.5, whereas the inactive analogue, 4 alpha-phorbol, did not have a Ca2+-sensitizing effect, nor did it increase AA and DAG levels.5. In the virtual absence of Ca2+ (pCa > 8) GTP gamma S also increased AA and DAG levels by 3.5- and 1.6-fold, respectively. The effect of free Ca2+ itself on AA and DAG release was modest in the physiological range (pCa 7.0 to pCa 6.0), but pCa 4.5 caused an approximately 3- to 4-fold increase in AA and DAG levels, compared with the levels at pCa 8. In permeabilized ileum smooth muscle maintained at constant [Ca2+] (pCa 6.0), carbachol also significantly increased AA to 1.75 times its original value within 1 min of its application.6. Our results are consistent with, although do not prove, the roles of AA and DAO as second and/or co-messenger(s) in smooth muscle, while the increases in AA and DAG levels induced by PDBu raise the possibility that they contribute to some of the cellular effects of phorbol esters.