OBJECTIVE: Obesity is an increasing problem in obstetric practice. Apelin, secreted by adipocytes, is present in increased serum concentrations in an obese state. Our group has previously highlighted that the adipokines leptin and ghrelin have a potential role in metabolic modulation of uterine contractility in obese women. The aim of this study was to evaluate the effects of apelin on human uterine contractility in vitro.STUDY DESIGN: Biopsies of human myometrium were obtained at elective cesarean section. Myometrial strips suspended under isometric conditions, undergoing spontaneous and oxytocin-induced contractions, were exposed to cumulative additions of apelin in the concentration range of 1 nmol/L to 1 mu mol/L. Control experiments were performed simultaneously.RESULTS: Apelin exerted an inhibitory effect on spontaneous and oxytocin induced contractions in human myometrium. The mean maximal inhibition values were 36.8 +/- 6.4% for spontaneous (n = 6; P = .002) and 30.4 +/- 4.6% for oxytocin-induced contractions (n = 6; P < .0001).CONCLUSION: Apelin inhibits human uterine contractility in vitro, raising the possibility that such metabolic modulation may play a physiological role in obese parturients.