OBJECTIVE: To study the effect of oxyhemoglobin (IIb), a scavenger of nitric oxide (NO), and DEA.NO, an NO donor, on isolated uterine and aortic rings from rats at mid and late gestation. STUDY DESIGN: Rings of uterus and thoracic aorta denuded of endothelium were obtained fiom Sprague-Dawley rats on day 14 and 21 of gestation and equilibrated at 2g passive tension for isometric recording in organ chambers filled with krebs-Henseleit solution bubbled with 5% CO2 in air (37°C, pH 7.35-7.4). Increasing concentrations of DEA.NO were added to the baths after 10 min pretreatment with Hb (10-5 M) or vehicle and the effects on spontaneously contracting uterine rings (10-6 to 10-4 M) and on aortic rings (10-9 to 10-6 M) precontracted with phenylephrine were determined. After reaching the highest concentration of DEA.NO, Hb (10-5 M) was again added to check for further scavenging effect. RESULTS: The relaxation of aortic rings by DEA.NO was concentration-dependent and significantly attenuated by pretreatment with Hb, with no significant difference in response noted between day 14 and 21. Spontaneous myometrial contractions on day 11 were inhibited by DEA.NO in a concentraion dependent manner and the effect was significantly attenuated by pretreatment with Hb. However, myometrial rhythmic activity on day 21 was not significantly affected by DEA.NO or Hb. When compared to aortic rings, the effect of DEA.NO on the myometrium was only seen at very high concentrations. Addition of Hb at the conclusion of the concentration response curve had additional scavenging effect in the aortic, but not uterine rings. CONCLUSIONS: In the rat, the myometrium is less sensitive to NO than the aorta and the effect of NO on myometrial, but not vascular, smooth muscle defends on gestational age. An NO-dependent mechanism may be important in maintaining uterine quiescence in pregnancy and a decrease in myometrial sensitivity to NO or increase in scavenging activity may contribute to the onset of labor.
|Original language||English (US)|
|Journal||Acta Diabetologica Latina|
|Issue number||1 PART II|
|State||Published - 1997|
ASJC Scopus subject areas
- Internal Medicine
- Endocrinology, Diabetes and Metabolism