Cyclic ADP-ribose/Ca2+ system in uterine smooth muscle cells

V. I. Tica, V. Cojocaru, O. S. Tica, S. Berceanu, A. A. Tica

Abstract: Ryanodine (Ry)-sensitive calcium stores can be activated by cyclic adenosine diphosphate ribose (cADPR) and by Ca2+ through Ca2+-induced Ca2+-release (CICR), both intracellular signaling pathways being initiated by almost all oxytocics. We investigated the role of Ry-sensitive calcium stores on spontaneous and angiotensin II (AGII)-induced uterine contraction by blocking Ry receptors with Ry in a rat model. From our knowledge, this is the first study on AGII effects on internal calcium mobilization, after cADPR pathway activation. The characteristics of myometrial contraction before and after Ry 10-6M administration were measured, using non pregnant female Sprague-Dawley rats (n=20) uterus.Results. Ry 10-6M did not influence spontaneous activity. Using Ry at 10-6M concentration, the amplitude and the frequency of AGII-induced contraction were showed to decrease with 11.62±4% and 9.78±3%, respectively. Our results suggest that one of the mechanisms through which angiotensin II induces an oxytocic effect is the mobilization of calcium from the calcium stores by activating the Ry-sensitive calcium channels.
Keywords: calcium stores, myometrium, angiotensin II, ryanodine, cADP ribose, rats