Yousufzai S Y, Abdel-Latif A A
Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta 30912, USA.
Eur J Pharmacol. 1998 Nov 6;360(2-3):185-93. doi: 10.1016/s0014-2999(98)00697-9.
We investigated the effects of the protein tyrosine kinase inhibitors, genistein, tyrphostin 47, and herbimycin on prostaglandin F2alpha- and carbachol-induced inositol-1,4,5-trisphosphate (IP3) production, [Ca2+]i mobilization and contraction in cat iris sphincter smooth muscle. Prostaglandin F2alpha and carbachol induced contraction in a concentration-dependent manner with EC50 values of 0.92 x 10(-9) and 1.75 x 10(-8) M, respectively. The protein tyrosine kinase inhibitors blocked the stimulatory effects of prostaglandin F2alpha, but not those evoked by carbachol, on IP3 accumulation, [Ca2+]i mobilization and contraction, suggesting involvement of protein tyrosine kinase activity in the physiological actions of the prostaglandin. Daidzein and tyrphostin A, inactive negative control compounds for genistein and tyrphostin 47, respectively, were without effect. Latanoprost, a prostaglandin F2alpha analog used as an antiglaucoma drug, induced contraction and this effect was blocked by genistein. Genistein (10 microM) markedly reduced (by 67%) prostaglandin F2alpha-stimulated increase in [Ca2+]i but had little effect on that of carbachol in cat iris sphincter smooth muscle cells. Vanadate, a potent inhibitor of protein tyrosine phosphatase, induced a slow gradual muscle contraction in a concentration-dependent manner with an EC50 of 82 microM and increased IP3 generation in a concentration-dependent manner with an EC50 of 90 microM. The effects of vanadate were abolished by genistein (10 microM). Wortmannin, a myosin light chain kinase inhibitor, reduced prostaglandin F2alpha- and carbachol-induced contraction, suggesting that the involvement of protein tyrosine kinase activity may lie upstream of the increases in [Ca2+]i evoked by prostaglandin F2alpha. Further studies aimed at elucidating the role of protein tyrosine kinase activity in the coupling mechanism between prostaglandin F2alpha receptor activation and increases in intracellular Ca2+ mobilization and identifying the tyrosine-phosphorylated substrates will provide important information about the role of protein tyrosine kinase in the mechanism of smooth muscle contraction, as well as about the mechanism of the intraocular pressure lowering effect of the prostaglandin in glaucoma patients.
我们研究了蛋白酪氨酸激酶抑制剂染料木黄酮、 tyrphostin 47 和除莠霉素对猫虹膜括约肌平滑肌中前列腺素 F2α 和卡巴胆碱诱导的肌醇 -1,4,5- 三磷酸（IP3）生成、[Ca2+]i 动员及收缩的影响。前列腺素 F2α 和卡巴胆碱以浓度依赖方式诱导收缩，其 EC50 值分别为 0.92×10(-9) 和 1.75×10(-8) M。蛋白酪氨酸激酶抑制剂阻断了前列腺素 F2α 对 IP3 积累、[Ca2+]i 动员及收缩的刺激作用，但不影响卡巴胆碱引起的这些作用，提示蛋白酪氨酸激酶活性参与了前列腺素的生理作用。黄豆苷元和 tyrphostin A 分别作为染料木黄酮和 tyrphostin 47 的无活性阴性对照化合物，无作用。拉坦前列素是一种用作抗青光眼药物的前列腺素 F2α 类似物，可诱导收缩，且该作用被染料木黄酮阻断。染料木黄酮（10 μM）显著降低（67%）了前列腺素 F2α 刺激的猫虹膜括约肌平滑肌细胞中 [Ca2+]i 的增加，但对卡巴胆碱引起的 [Ca2+]i 增加影响很小。钒酸盐是一种有效的蛋白酪氨酸磷酸酶抑制剂，以浓度依赖方式诱导缓慢渐进性肌肉收缩，EC50 为 82 μM，并以浓度依赖方式增加 IP3 生成，EC50 为 90 μM。染料木黄酮（10 μM）消除了钒酸盐的作用。渥曼青霉素是一种肌球蛋白轻链激酶抑制剂，可降低前列腺素 F2α 和卡巴胆碱诱导的收缩，提示蛋白酪氨酸激酶活性的参与可能位于前列腺素 F2α 引起的 [Ca2+]i 增加的上游。旨在阐明蛋白酪氨酸激酶活性在前列腺素 F2α 受体激活与细胞内 Ca2+ 动员增加之间偶联机制中的作用以及鉴定酪氨酸磷酸化底物的进一步研究，将为蛋白酪氨酸激酶在平滑肌收缩机制中的作用以及前列腺素在青光眼患者眼压降低作用机制提供重要信息。
