In vitro study of carbetocin, an oxytocin receptor agonist, and 4-phenylfuroxan-3-carbonitrile, a NO-releasing agent, as cervical dilatators in sheep.

The aim was to study the effect of 4-phenylfuroxan-3-carbonitrile (Fx), a NO-releasing agent, and carbetocin, an oxytocin receptor agonist, on matrix metalloproteinases-2 (MMP-2) activity and PGE2 production in cervix from cycling sheep. Cervical explants were incubated during 12 h with MEM supplemented with increasing concentrations of Fx in DMSO (2 %) (0 to 300 μg/mL) with Cb (100 ng/mL) (Experiment 1, n = 15) and DMSO (2 %), DMSO + Cb (100 ng/mL) or DMSO + Fx (30 μg/mL) (Experiment 2, n = 10), and their respective controls. In the supernatants, activated (A) and latent (L) MMP-2 activities were determined by a SDS-PAGE zymography, PGE2 concentration by immunoassay and NO production indirectly as nitrites by spectrophotometry. Data were analyzed by ANOVA. The Cb treatment increase the A MMP-2 activity in DMSO (Experiment 1 at follicular phase and Experiment 2) or alone (Experiment 2) and increase the L MMP-2 activity (Experiments 1 and 2) (P < 0.02). The DMSO treatment also increase the L MMP2 activity (Experiment 2) (P < 0.0001). Treatment with Fx + DMSO increased the concentration of accumulated nitrites in the supernatant (P < 0.0001) (Experiment 1), but did not affect or decrease the activity of A and L MMP-2 (P < 0.04) (Experiments 1 and 2). The PGE2 concentration trend to increase with Cb treatment (P = 0.0614) and decrease with Fx+DMSO treatment (P < 0.0001) (Experiment 2). In conclusion, Cb and/or DMSO treatment of cervical explants increase the MMP-2 activity through PGE2-independent mechanisms, but Fx in DMSO fail in this, suggesting that the pre-treatment with Cb and/or DMSO could be used to increase cervical dilation in ewes.