Gynecology & Obstetrics
Open Access

Abstract

Relaxant Effect of Cyppa In Vitro and Expression Analysis of SK3 Splice Variants in the Myometrium of Pregnant and Non-Pregnant Women

Rosenbaum ST, Svalo J, Larsen T, Joergensen J and Bouchelouche P

Background and objective: We have recently shown an overall down-regulation of SK3 channels in pregnant human myometrium compared to non-pregnant myometrium. The aim of this study was to investigate whether SK3 splice variants are involved in the down-regulation of SK3 channels. We also tested whether SK channels are implicated in myometrial contractility using CyPPA, a novel and selective SK2 and SK3 channel activator.

Study design: We evaluated the expression of SK3 splice variants at mRNA level by qRT-PCR in myometrium from pregnant (n=11) and non-pregnant (n=11) women. Isometric tension recordings were performed to assess human myometrial contractility on biopsies obtained at elective caesarean section at term (n=6) and from hysterectomy (n=6). We investigated the effects of CyPPA (0.1-60 μM) on spontaneous contractions.

Results: The relative quantity of SK3 variant 3 did not differ between myometrium from pregnant and non-pregnant women (P=0.332). Variant 2 was not found present at detectable amounts. In contrast, SK3 variant 1 showed a 3-fold down-regulation in pregnant compared to non-pregnant myometrium (P=0.002).

CyPPA depressed spontaneous phasic contractions in human myometrial strips of both non-pregnant and pregnant origin. It took place in a concentration-dependent manner (where pIC50 = 5.02 ± 0.08 and 5.16 ± 0.15, respectively, and P>0.05), with contractions being abolished at 60 μM CyPPA.

Conclusions: We have been successful in demonstrating the presence of SK3 splice variants in human myometrium, for the first time. We also show that SK3 variant 1 is down-regulated in pregnant myometrium, and that it may be responsible for the overall down-regulation of SK3 channels observed in pregnant, as compared to nonpregnant, human myometrium. CyPPA exerts a potent relaxant effect on human myometrial tissue. This suggests that SK3 channels may be a new pharmacological target for the development of tocolytica.