[Inhibition of uterine contractions: new in vitro pharmacological approaches on the pregnant human myometrium]

The aim of this study was to evaluate the in vitro effects of phosphodiesterase 4 inhibitors (PDE4I) and their combination with salbutamol (beta 2-adrenoceptor agonist) on spontaneous contractions and to investigate by in vitro and biochemical studies and analysis of mRNA expression the presence of beta 3-adrenoceptor in human near-term myometrium. Rolipram, RP 73401 and Ro 20-1724 (PDE4I) inhibited spontaneous myometrial contractions (Emax approximately 100 per cent; pD2 approximately 6.80 for the two first and 6.31 for Ro 20-1724). Rolipram 10(-8) M potentiated the response to salbutamol (Emax = 88 per cent vs. 40 per cent and pD2 = 6.93 and 6.36 with or without rolipram respectively). SR 59119A, a beta 3-adrenoceptor agonist, was more efficient than salbutamol in inhibiting the contractions (Emax 52 per cent and 27 per cent respectively, p0.05) but they both induced a significant increase of cAMP production. In both functional and biochemical studies, SR 59119A was only antagonized by the beta 3-adrenoceptor antagonist SR 59230A. The beta 3-AR mRNA was positively expressed in myometrium preparations in a reverse transcription polymerase chain assay. In conclusion, phosphodiesterase 4 inhibitors alone or combined with beta 2-adrenoceptor agonists and beta 3-adrenoceptor agonists might have potential interest as tocolytic agents.