Ho K M, McMurray G, Brading A F, Noble J G, Ny L, Andersson K E
Department of Urology, Churchill Hospital, Oxford, United Kingdom.
J Urol. 1998 Mar;159(3):1091-6.
Nitric oxide (NO) is known to relax urethral smooth muscle. The role of NO in the control of urethral striated muscle remains unknown. We have investigated the distribution of nitric oxide synthase (NOS) immunoreactivity and its possible relationship with subtypes of intramural striated muscle fibers in the human male membranous urethra.
Whole transverse cryostat sections from seven membranous urethrae were studied using NOS immunohistochemistry and NADPH diaphorase histochemistry. Striated fiber subtypes were demonstrated using immunohistochemistry for troponin T and histochemistry for myofibrillary adenosine triphosphatase (ATPase). Consecutive sections were used to assess the correlation between the distribution of NOS immunoreactivity and the type of striated fibers.
NOS immunoreactivity and NADPH diaphorase activity were detected in the sarcolemma of 48.5% of the intramural striated muscle fibers. NOS immunoreactive nerve trunks and fine nerve fibers, a few of which appeared to end on muscle fibers, were present in the striated sphincter. Fast twitch fibers were detected by ATPase staining, and also exhibited positive immunoreactivity for troponin T, constituting 34.6% of the total number of striated fibers. Two populations of slow twitch fibers were identified; one with small diameter (mean: 15.7 microns) and another of larger diameter (mean: 21.7 microns) comparable to that of fast twitch fibers. 86% of the fast twitch fibers and 29% of slow twitch fibers (most of which had larger diameters) exhibited NOS immunoreactivity and NADPH diaphorase activity in the sarcolemma.
The presence of nitrergic nerve fibers in the striated urethral sphincter suggests an involvement in the innervation of urethral striated muscle. Furthermore, the presence of NOS immunoreactivity in the sarcolemma may indicate a role for NO in the regulation of urethral striated muscle metabolism and contraction.
已知一氧化氮（NO）可使尿道平滑肌松弛。NO在控制尿道横纹肌中的作用尚不清楚。我们研究了一氧化氮合酶（NOS）免疫反应性的分布及其与人类男性膜部尿道壁内横纹肌纤维亚型的可能关系。
使用NOS免疫组织化学和NADPH黄递酶组织化学研究了7个膜部尿道的全层横向冰冻切片。使用肌钙蛋白T免疫组织化学和肌原纤维三磷酸腺苷酶（ATP酶）组织化学来显示横纹肌纤维亚型。连续切片用于评估NOS免疫反应性分布与横纹肌纤维类型之间的相关性。
在48.5%的壁内横纹肌纤维的肌膜中检测到NOS免疫反应性和NADPH黄递酶活性。在横纹括约肌中存在NOS免疫反应性神经干和细神经纤维，其中一些似乎终止于肌纤维上。通过ATP酶染色检测到快肌纤维，并且它们对肌钙蛋白T也表现出阳性免疫反应性，占横纹肌纤维总数的34.6%。鉴定出两类慢肌纤维；一类直径较小（平均：15.7微米），另一类直径较大（平均：21.7微米），与快肌纤维相当。86%的快肌纤维和29%的慢肌纤维（其中大多数直径较大）在肌膜中表现出NOS免疫反应性和NADPH黄递酶活性。
尿道横纹括约肌中存在含氮能神经纤维提示其参与尿道横纹肌的神经支配。此外，肌膜中存在NOS免疫反应性可能表明NO在调节尿道横纹肌代谢和收缩中起作用。
