Pharmacological and biochemical study on the effects of selective phosphodiesterase inhibitors on human term myometrium

Abstract

This study was aimed at evaluating the in vitro effects of phosphodiesterase inhibitors and beta2-adrenoceptor agonists on spontaneous contractions of human term myometrium. Rolipram, RP 73401 (3-cyclopentyloxy-N-(3,5(-dichloro-4-pyridil)-4-methoxybenzamide) and Ro 20-1724 (1-4-(3-butoxy-4-methoxybenzyl)-2-imidozolidinone) (phosphodiesterase 4 inhibitors) inhibited spontaneous myometrial contractions (Emax approximately 100%; pD2 of 6.80+/-0.28, 6.84+/-0.32 and 6.31+/-0.03, respectively). Salbutamol and formoterol were less effective (Emax=40+/-6% and 35+/-12%, respectively) than phosphodiesterase 4 inhibitors to reduce myometrial contractility. Inhibitors of phosphodiesterase 3 (milrinone and siguazodan) and 5 (zaprinast) were marginally effective. Rolipram (10-30 nM) and siguazodan (0.1 microM) potentiated the response to salbutamol (Emax=75+/-12%, 88+/-8% and 73+/-12% and pD2=6.51+/-0.20, 6.93+/-0.29 and 6.48+/-0.16, respectively). Sodium nitroprusside (pD2=6.76+/-0.29) and theophylline (pD2=5.15+/-0.22) were effective inhibitors of myometrial contractions. Chromatographic separation of phosphodiesterase isoenzymes demonstrated that phosphodiesterase 4 is predominant but other phosphodiesterase isoenzymes were also identified. In conclusion, phosphodiesterase 4 inhibitors alone or combined with beta2-adrenoceptor agonists have potential interest as tocolytic agents.

The human near‐term myometrial β3‐adrenoceptor but not the β2‐adrenoceptor is resistant to desensitisation after sustained agonist stimulation

“…cAMP levels (expressed as pmol mg À1 protein) were determined after agonist pretreatments, and were compared with those obtained in time-matched paired strips incubated either in Krebs solution alone (basal value) or in Krebs solution containing the respective solvents of each agonist (solvent value). Tissues were then processed as previously reported by Bardou et al (1999). The samples were immediately transferred into liquid nitrogen and homogenised in ice-cold 10% trichloroacetic acid.…”

“…Interestingly, the implication of an upregulation of PDE4 in the adaptation of myometrium to long-term treatment with b 2 -AR has been emphasised by Mehats et al (1999). Furthermore, Bardou et al (1999) and Mehats et al (2001) have both shown that pretreatment of myometrial strips of women at term with a PDE4-selective inhibitor potentiates the relaxant effect of salbutamol. In our model, the long-term exposure of myometrial strips to salbutamol did not modify the PDE4 activity.…”

“…PDE families represent the sole mechanism for inactivating cAMP or cGMP (Conti et al, 2003;Houslay & Adams, 2003). In human myometrium, among the five PDE families represented, it is now well established that the PDE4 family, specific for cAMP hydrolysis and inducible by its own substrate cAMP, is predominantly expressed (Leroy et al, 1989;Bardou et al, 1999). There is now defined evidence that cAMP induces an upregulation of PDE4, accelerating the degradation of this cyclic nucleotide (Perry et al, 2002).…”

5-HT3 receptor antagonists do not alter spontaneous contraction of pregnant myometrium in vitro

“…[19][20][21] Parturients underwent spinal anesthesia for cesarean delivery. After delivery of the fetus and placenta, and before oxytocin administration, a small piece of the myometrium was removed from the upper midline portion of the uterine incision in the lower uterine segment.…”

Characterization of Serotonin Receptors in Pregnant Human Myometrium

“…The muscle tissue was dissected further, in ice-cold Krebs' solution, into longitudinal strips (following the plane of the muscle fibers) of approximately 1 to 3 ϫ 8 to 12 mm. Tissue strips were mounted in the organ bath, secured with cotton thread and placed under 2-g tension (Bardou et al, 1999), and allowed to equilibrate for a period of 90 min. Organ bath chambers were filled with Krebs' solution, which was warmed to 37°C and gassed with 95% O 2 /5% CO 2 .…”