Measurement of muscle protein synthesis by positron emission tomography with L-[methyl-11C]methionine:: Effects of transamination and transmethylation
Measurement of muscle protein synthesis by positron emission tomography with L-[methyl-11C]methionine:: Effects of transamination and transmethylation
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DOI：
10.1097/00005373-199908000-00021
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发表时间：
1999-08-01
影响因子：
--
通讯作者：
Fischman, AJ
中科院分区：
文献类型：
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作者：
Carter, EA;Yu, YM;Fischman, AJ
背景：L-[甲基-(11)C]蛋氨酸正电子发射断层扫描提供了一种骨骼肌局部蛋白质合成率的测量方法。然而，该方法的有效性取决于通过最小的转氨基和/或转甲基化将蛋氨酸结合到蛋白质中。为了直接验证这些假设，测量了对照组和放线菌亚胺处理组大鼠骨骼肌对L-[甲基-(14)C]蛋氨酸的摄取。方法：正常和放线菌亚胺处理组大鼠(n=8/组)注射50mU的L-[甲基-(14)C]蛋氨酸，并采集动脉血90分钟。处死大鼠后，取大腿肌肉匀浆，离心，三氯乙酸处理。从三氯乙酸的可沉淀性、动脉时间-活度曲线和血浆蛋氨酸浓度估算循环中蛋氨酸的PSR。结果：在正常大鼠的组织中，接近70%的放射性是由三氯乙酸沉淀的。在正常动物中，PSR为0.22nmol.min(-1).g(-1)，与以前的结果非常一致。环己胺处理组的PSR为0.0032 nmol.min(-1).g(-1)，与对照组相比下降了98%。结论：这些研究支持了L-[甲基-(11(14)C]蛋氨酸]以(11(14))C标记蛋白的形式在骨骼肌中积累的假说。
Background: Positron emission tomography with L-[methyl-(11)C]methionine provides a measure of regional protein synthesis rate (PSR) in skeletal muscle. However, the validity of the method depends on incorporation of methionine into protein with minimal transamination, transmethylation, or both. To test directly these assumptions, uptake of L-[methyl-(14)C]methionine in skeletal muscle was measured in control and cycloheximide-treated rats.Methods: Normal and cycloheximide-treated rats (n = 8/group) were injected with 50 mu Ci of L-[methyl-(14)C]methionine and arterial blood sampled over 90 minutes. After killing, thigh muscle was homogenized, centrifuged, and treated with trichloroacetic acid. PSR from circulating methionine was estimated from trichloroacetic acid-precipitable radioactivity, arterial time-activity curves, and plasma methionine concentrations.Results: In normal rats, similar to 70% of the tissue radioactivity was precipitated with trichloroacetic acid. In normal animals, PSR was 0.22 nmoles.min(-1).g(-1), in excellent agreement with previous results. In the cyclohexamide-treated group, PSR was 0.0032 nmoles.min(-1).g(-1); similar to 98% reduction compared with controls.Conclusion: These studies support the hypothesis that L-[methyl-(11(14))C]methionine accumulates in skeletal muscle as (11(14))C-labeled protein.