<p>Uterine motility depends on the formation of the contractile protein actomyosin under the influence of the Ca2+&nbsp;dependent phosphorylating enzyme myosin light-chain kinase. Oxytocin promotes contractions by increasing the intracellular Ca2+, which in turn activates myosin&#39;s light chain kinase. Oxytocin has specific receptors in the muscle lining of the uterus and the receptor concentration increases greatly during pregnancy, reaching a maximum in early labor at term.</p>