Effects of beta-sitosterol on isolated human non-pregnant uterus in comparison to prostaglandin E2

Abstract

Background: Beta-sitosterol (β-sitosterol) is one of the several phytosterols widely studied for its potential to reduce benign prostatic hyperplasia and blood cholesterol levels. Objective: In the present study, the effects of β-sitosterol on spontaneous and agonist-induced contractions in in vitro nonpregnant human uterus with respect to prostaglandin E2(PGE2) were investigated. Materials and Methods: Myometrial strips, measuring approximately 15 mm × 4 mm × 2 mm, were attained from hysterectomy samples of premenopausal women. Longitudinal muscle strips were mounted on tissue baths, under physiological conditions, to measure their isometric contraction. The effects of cumulative amounts of β-sitosterol on spontaneous motility in the absence and presence of prazosin, atropine, fulvestran, indomethacin, or ethylenediaminetetraacetic acid (EDTA), and on agonist-induced motor activity, were examined. Results: On strips in the follicular phase, both β-sitosterol (1–100 μg/ml) and PGE2(0.1–10 μg/ml) increase, in a concentration-dependent manner, muscular basic tonus and amplitude and frequency of spontaneous uterine contractions; whereas on strips obtained during periovulatory phase, β-sitosterol and PGE2cause inhibition of uterine motility. For contractile response, the effective concentrations (EC50) were 47.8 μg/ml and 5.19 μg/ml, respectively. Unlike indomethacin, the tissue pretreatment with prazosin, fulvestran, atropine, or ethylenediaminetetraacetic acid did not affect the contractile uterine responses to β-sitosterol. Furthermore, the β-sitosterol was able to potentiate the contractile response induced by acetylcholine and vasopressin. Conclusions: These observations suggest that β-sitosterol may be a useful modulator of the uterine motility during menstrual cycle, facilitating female fertility.