Proceedings of The Physiological Society
University of Oxford (2011) Proc Physiol Soc 23, PC237
In Vitro Effect of Apelin on Spontaneous Contractions in the Rat Myometrium
E. Kacar1, Z. Ercan1, S. Kutlu1, M. Ozcan2, S. Canpolat3, A. Ayar3
1. Department of Physiology, Firat University, Faculty of Medicine, Elazig, Turkey. 2. Department of Biophysics, Firat University, Faculty of Medicine, Elazig, Turkey. 3. Department of Physiology, Karadeniz Thechnical University, Faculty of Medicine, Trabzon, Turkey.
Apelin is a novel bioactive peptide as the endogenous ligand for the orphan G-protein-coupled receptor, APJ. Expression of both apelin and APJ are determined in various tissues such as hypothalamus, lung, uterus, ovary and the gastrointestinal tract in rat. Though some different molecular forms of apelin are turned out in tissues, apelin-13 is one of the most effective forms of apelin peptides. In this study we investigated the effect of apelin-13 on spontaneous contractions in the rat uterus in vitro. Myometrium strips were removed from adult Wistar rats both in dioestrus and 21st day of pregnancy following decapitation and placed in a jacked tissue bath containing Krebs solution at 37 oC and pH 7.4, constantly bubbled with 95% oxygen and 5% carbon dioxide. The myometrial strips were allowed to equlibrate under 1g tension and isometric contractions were measured by force displacement transducer. After diminishing of spontaneous contractions, control contractions were recorded for 10 min and increasing concentrations of apelin were added to the tissue bath cumulatively. The amplitude and frequencies (number of contractions for 10-minute period) of contractions were evaluated at 10-min interval before and after applications of apelin and determined as mean±SEM. One Way ANOVA was used for statistical analysis. Apelin stimulated the spontaneous contractions in myometrial strips. The mean frequency of contractions were 1.14±0.14 (n=6), 1.00±0.00 (n=6), 1.00±0.00 (n=6), 2.57±0.30 and 4.14±0.70 (n=6) in dioestrus group and 1.17±0.17 (n=7), 1.17±0.17 (n=7), 3.33+0.80 (n=7), 4.83+0.87 (n=7) and 5.33+0.99 (n=7) in late pregnant group under control conditions and after application of 0.01μM, 0.1μM, 1μM and 10μM apelin, respectively. The increases in frequency of contractions were significant in 1μM and 10μM apelin for strips from both dioestrus (p<0.05 and p<0.001, respectively) and late pregnant rats (p<0.01, for both two concentrations). The mean peak amplitudes (gram) of contractions were 1.47±0.05 (n=6), 1.45±0.06 (n=6), 1.50±0.05 (n=6), 1.73±0.06 (n=6) and 1.91±0.10 (n=6) in dioestrus group and 2.03±0.12 (n=7), 2.03±0.12 (n=7), 2.56±0.20 (n=7), 3.01±0.27 (n=7) and 3.12±0.22 (n=7) in late pregnant rat under control conditions and after application of 0.01μM, 0.1μM, 1μM and 10μM apelin, respectively. The increase in amplitude of contractions were significant after application of 10μM apelin in strips from rats at dioestrus (p<0.01) and 1μM and 10μM apelin in late pregnant rat (p<0.05 and p<0.01, respectively). In this study, we demonstrate for the first time that apelin has stimulatory effect on myometrial contractility in rats. Further detailed investigations are needed to clarify the exact mechanism(s) of apelin induction on myometrium contractility and the role of apelin in pregnancy and parturition processes.
Where applicable, experiments conform with Society ethical requirements