Baccari Maria Caterina, Nistri Silvia, Quattrone Silvia, Bigazzi Mario, Bani Sacchi Tatiana, Calamai Franco, Bani Daniele
Departments of Physiological Sciences and Anatomy,4, University of Florence, Florence, Italy.
Biol Reprod. 2004 Jan;70(1):222-8. doi: 10.1095/biolreprod.103.018374. Epub 2003 Oct 1.
The peptide hormone relaxin, which attains high circulating levels during pregnancy, has been shown to depress small-bowel motility through a nitric oxide (NO)-mediated mechanism. In the present study we investigated whether relaxin also influences gastric contractile responses in mice. Female mice in proestrus or estrus were treated for 18 h with relaxin (1 microg s.c.) or vehicle (controls). Mechanical responses of gastric fundal strips were recorded via force-displacement transducers. Evaluation of the expression of nitric oxide synthase (NOS) isoforms was performed by immunohistochemistry and Western blot. In control mice, neurally induced contractile responses elicited by electrical field stimulation (EFS) were reduced in amplitude by addition of relaxin to the organ bath medium. In the presence of the NO synthesis inhibitor l-NNA, relaxin was ineffective. Direct smooth muscle contractile responses were not influenced by relaxin or l-NNA. In strips from relaxin-pretreated mice, the amplitude of neurally induced contractile responses was also reduced in respect to the controls, while that of direct smooth muscle contractions was not. Further addition of relaxin to the bath medium did not influence EFS-induced responses, whereas l-NNA did. An increased expression of NOS I and NOS III was observed in gastric tissues from relaxin-pretreated mice. In conclusion, the peptide hormone relaxin depresses cholinergic contractile responses in the mouse gastric fundus by up-regulating NO biosynthesis at the neural level.
肽类激素松弛素在孕期循环水平会升高，研究表明它可通过一氧化氮（NO）介导的机制抑制小肠蠕动。在本研究中，我们探究了松弛素是否也会影响小鼠的胃收缩反应。对处于动情前期或动情期的雌性小鼠皮下注射松弛素（1微克）或赋形剂（对照组），持续18小时。通过力-位移传感器记录胃底条带的机械反应。采用免疫组织化学和蛋白质印迹法评估一氧化氮合酶（NOS）同工型的表达。在对照小鼠中，向器官浴液中添加松弛素会降低电场刺激（EFS）诱发的神经源性收缩反应的幅度。在存在NO合成抑制剂L-NNA的情况下，松弛素无效。直接的平滑肌收缩反应不受松弛素或L-NNA的影响。在经松弛素预处理的小鼠的条带中，神经源性收缩反应的幅度相对于对照组也降低了，而直接平滑肌收缩的幅度则没有。向浴液中进一步添加松弛素不影响EFS诱发的反应，而L-NNA则有影响。在经松弛素预处理的小鼠的胃组织中观察到NOS I和NOS III的表达增加。总之，肽类激素松弛素通过在神经水平上调NO生物合成来抑制小鼠胃底的胆碱能收缩反应。
