Muthuchamy Mariappan, Gashev Anatoliy, Boswell Niven, Dawson Nancy, Zawieja David
Department of Medical Physiology, Cardiovascular Research Institute, College of Medicine-Texas A&M University System Health Science Center, College Station, Texas 77843-1114, USA.
FASEB J. 2003 May;17(8):920-2. doi: 10.1096/fj.02-0626fje. Epub 2003 Mar 28.
Lymphatics are necessary for the generation and regulation of lymph flow. Lymphatics use phasic contractions and extrinsic compressions to generate flow; tonic contractions alter resistance. Lymphatic muscle exhibits important differences from typical vascular smooth muscle. In this study, the thoracic duct exhibited significant functional differences from mesenteric lymphatics. To understand the molecular basis for these differences, we examined the profiles of contractile proteins and their messages in mesenteric lymphatics, thoracic duct, and arterioles. Results demonstrated that mesenteric lymphatics express only SMB smooth muscle myosin heavy chain (SM-MHC), whereas thoracic duct and arterioles expressed both SMA and SMB isoforms. Both SM1 and SM2 isoforms of SM-MHC were detected in arterioles and mesenteric and thoracic lymphatics. In addition, the fetal cardiac/skeletal slow-twitch muscle-specific beta-MHC message was detected only in mesenteric lymphatics. All four actin messages, cardiac alpha-actin, vascular alpha-actin, enteric gamma-actin, and skeletal alpha-actin, were present in both mesenteric lymphatics and arterioles. However, in thoracic duct, predominantly cardiac alpha-actin and vascular alpha-actin were found. Western blot and immunohistochemical analyses corroborated the mRNA studies. However, in arterioles only vascular alpha-actin protein was detected. These data indicate that lymphatics display genotypic and phenotypic characteristics of vascular, cardiac, and visceral myocytes, which are needed to fulfill the unique roles of the lymphatic system.
淋巴管对于淋巴液流动的产生和调节是必不可少的。淋巴管利用阶段性收缩和外部压迫来产生流动；持续性收缩改变阻力。淋巴肌与典型的血管平滑肌存在重要差异。在本研究中，胸导管与肠系膜淋巴管表现出显著的功能差异。为了解这些差异的分子基础，我们检测了肠系膜淋巴管、胸导管和小动脉中收缩蛋白及其信使核糖核酸的表达谱。结果表明，肠系膜淋巴管仅表达SMB平滑肌肌球蛋白重链（SM-MHC），而胸导管和小动脉则同时表达SMA和SMB亚型。在小动脉、肠系膜和胸淋巴管中均检测到SM-MHC的SM1和SM2亚型。此外，仅在肠系膜淋巴管中检测到胎儿心脏/骨骼肌慢肌特异性β-MHC信使核糖核酸。肠系膜淋巴管和小动脉中均存在所有四种肌动蛋白信使核糖核酸，即心脏α-肌动蛋白、血管α-肌动蛋白、肠γ-肌动蛋白和骨骼肌α-肌动蛋白。然而，在胸导管中，主要发现的是心脏α-肌动蛋白和血管α-肌动蛋白。蛋白质免疫印迹和免疫组织化学分析证实了信使核糖核酸研究结果。然而，在小动脉中仅检测到血管α-肌动蛋白蛋白。这些数据表明，淋巴管表现出血管、心脏和内脏肌细胞的基因型和表型特征，这是淋巴系统发挥独特作用所必需的。
