Both soluble guanylate cyclase and particulate guanylate cyclase regulate myometrial contractility, ,

OBJECTIVE: Our purpose was to compare the effects of agents stimulating particulate and soluble guanylate cyclase with spontaneous rat uterine contractions at midgestation and term. STUDY DESIGN: Uterine rings from midgestation (day 13) and term nonlaboring (day 22) rats were positioned in organ chambers for isometric force recording. Rings were treated with increasing concentrations of atrial natriuretic peptide, permeable analogs of cyclic guanosine monophosphate, and diethylamine/nitric oxide. RESULTS: Atrial natriuretic peptide was more effective in inhibition of uterine contractions than diethylamine/nitric oxide. The 50% inhibitory concentrations were –7.4 ± 0.12 and –7.38 ± 0.11 for atrial natriuretic peptide and –5.68 ± 0.09 and –4.23 ± 0.12 for diethylamine/nitric oxide at midgestation and term, respectively. Pretreatment of uterine rings with atrial natriuretic peptide significantly attenuated inhibition of spontaneous contractions by diethylamine/nitric oxide at midgestation. CONCLUSIONS: Uterine spontaneous contractions are influenced by both soluble and particulate guanylate cyclase; the former, but not latter, is gestational age dependent. (Am J Obstet Gynecol 1998;179:111-6.)