Contractile effects of endothelins on isolated ampullar segment of human oviduct in luteal phase of menstrual cycle

Endothelin-1 induces contractions of human oviduct ampullar segment in follicular phase of menstrual cycle, acting on ETA receptors. The aim of our study was to investigate effects of endothelin-1, endothelin-2 and endothelin-3 on isolated ampullar segment of human oviducts, taken from the patients in luteal phase of menstrual cycle. Fallopian tubes were taken from 20 female patients (one tube from each patient) during abdominal hysterectomy with adnexectomy, due to extensive uterine fibroids. The oviduct ampulla was mounted in an organ bath longitudinally, and the tension of the isolated preparation was recorded with the isometric transducer. Endothelin-1 produced concentration-dependent tonic contraction of the isolated ampullar segment (EC50 = 6.80 ± 1.2 × 10−10 M), and concentration-dependent inhibition of its rhythmic contractions (EC50 = 7.86 ± 2.3 × 10−10 M). Endothelin-2 produced concentration-dependent tonic contraction of the isolated ampullar segment (EC50 = 4.56 ± 0.3 × 10−10 M), without affecting its rhythmic contractions. Endothelin-3 did not affect either tone or rhythmic contractions of the isolated preparations. Selective antagonist for ETA receptor subtype, BQ 123, produced inhibition of endothelin-1 effects on both tone (pA2 = 9.50) and spontaneous rhythmic contractions (pA2 = 10.73), while selective antagonist for ETB receptor subtype, BQ 788, produced only inhibition of endothelin-1 effects on tone (pA2 = 9.61), while the effect of endothelin-1 on spontaneous rhythmic contractions remained unaffected. The results of our study suggest that in the luteal phase both ETA and ETB receptors regulate tone, and only ETA receptors regulate rhythmic activity of human oviduct's ampullar segment.