Jankowski Ron J, Prantil Rachelle L, Chancellor Michael B, de Groat William C, Huard Johnny, Vorp David A
Vascular Tissue Engineering Research Laboratories, Rm. 236, Cellomics Bldg., McGowan Institute for Regenerative Medicine, 100 Technology Drive, Pittsburgh, PA 15219, USA.
Am J Physiol Renal Physiol. 2006 May;290(5):F1127-34. doi: 10.1152/ajprenal.00330.2005. Epub 2005 Dec 20.
Rigorous study of the associations between urethral structural anatomy and biomechanical function is necessary to advance the understanding of the development, progression, and treatment of urethral pathologies. An ex vivo model was utilized to define the relative biomechanical contributions of the active (muscle) elements of the female urethra relative to its passive (noncontractile) elements. Whole urethras from female, adult rats were tested under a range of applied intraluminal pressures (0 to 20 mmHg) as a laser micrometer simultaneously measured midurethral outer diameter. Active tissue characterization was performed during induced contraction of either smooth muscle alone (N(omega)-nitro-l-arginine, phenylephrine), striated muscle alone (sodium nitroprusside, atropine, hexamethonium, acetylcholine), or during collective activation of both muscles (N(omega)-nitro-l-arginine, phenylephrine, acetylcholine). The subsequent collection of paired passive biomechanical responses permitted the determination of parameters related to intrinsic muscle contractile function. Activation of each muscle layer significantly influenced the biomechanical responses of the tissue. Measures of muscle responsiveness over a wide range of sustained opposing pressures indicated that an activated striated muscle component was approximately one-third as effective as activated smooth muscle in resisting tissue deformation. The maximum circumferential stress generated by the striated muscle component under these conditions was also determined to be approximately one-third of that generated by the smooth muscle (748 +/- 379 vs. 2,229 +/- 409 N/m(2)). The experiments quantitatively reveal the relative influence of the intrinsic urethral smooth and striated muscle layers with regard to their effect on the mechanical properties and maximum functional responses of the urethra to applied intralumenal stresses in the complete absence of extrinsic influences.
对尿道结构解剖与生物力学功能之间的关联进行严谨研究，对于增进对尿道疾病的发生、发展及治疗的理解十分必要。利用离体模型来确定雌性尿道的主动（肌肉）成分相对于其被动（非收缩性）成分的相对生物力学贡献。对成年雌性大鼠的整个尿道在一系列腔内压力（0至20 mmHg）下进行测试，同时用激光测微仪测量尿道中段外径。在单独诱导平滑肌收缩（N（ω）-硝基-L-精氨酸、去氧肾上腺素）、单独诱导横纹肌收缩（硝普钠、阿托品、六甲铵、乙酰胆碱）或同时诱导两种肌肉收缩（N（ω）-硝基-L-精氨酸、去氧肾上腺素、乙酰胆碱）期间进行主动组织特征分析。随后收集配对的被动生物力学反应，从而能够确定与内在肌肉收缩功能相关的参数。每个肌肉层的激活均显著影响组织生物力学反应。在广泛的持续对抗压力范围内对肌肉反应性的测量表明，激活的横纹肌成分在抵抗组织变形方面的效果约为激活的平滑肌的三分之一。在这些条件下，横纹肌成分产生的最大周向应力也被确定约为平滑肌产生的最大周向应力的三分之一（748±379对2229±409 N/m²）。这些实验定量揭示了在完全不存在外在影响的情况下，尿道内在平滑肌层和横纹肌层对尿道力学性能以及尿道对施加的腔内应力的最大功能反应的相对影响。
