BOTH SOLUBLE GUANYLATE-CYCLASE AND PARTICULATE GUANYLATE-CYCLASE REGULATE MYOMETRIAL CONTRACTILITY

OBJECTIVE: Our purpose was to compare the effects of agents stimulatin g particulate and soluble guanylate cyclase with spontaneous rat uteri ne contractions at midgestation and term. STUDY DESIGN: Uterine rings from midgestation (day 13) and term nonlaboring (day 22) rats were pos itioned in organ chambers for isometric force recording. Rings were tr eated with increasing concentrations of atrial natriuretic peptide, pe rmeable analogs of cyclic guanosine monophosphate, and diethylamine/ni tric 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 f or atrial natriuretic peptide and -5.68 +/- 0.09 and -4.23 +/- 0.12 fo r diethylamine/nitric oxide at midgestation and term; respectively. Pr etreatment of uterine rings with atrial natriuretic peptide significan tly attenuated inhibition of spontaneous contractions by diethylamine/ nitric oxide at midgestation. CONCLUSIONS: Uterine spontaneous contrac tions are influenced by both soluble and particulate guanylate cyclase ; the former, but not latter, is gestational age dependent.