Metabolic inhibition and contractions in isolated rat myometrium: The role of intracellular calcium homeostasis.

The aim of this study was to investigate the role of changes inintracellular calcium homeostasis metabolic stress (induced by chemicalhypoxia) on contractility of myometrium. Myometrial strips were isolatedfrom virgin Sprague Dawley rats after dislocation and suspended in onisolated tissue bath containing Krebs solution continuously bubbled with%95 O2 and %5 CO2 maintained at 37 C°? de (pH 7.4). After manifestationof spontaneous contractions were equilibrated under resting tensiondantrolene-Na, ethylene glycol tetra acetic acide (EGTA), dinitrophenole(DNP) and potassium cyanide (KCN) were applied to the tissue bath. Theamplitude and frequency of contractions were evaluated by 10-minintervals. Student-t test was used for statically analysis of data. Addingeither DNP (0.8 mM, n=8) or KCN (0.3 mM, n=8) to tissue bath caused arapid inhibition in KCl induced myometrium contractions. Application ofdantrolene-Na (10 µM) and EGTA (1 mM) caused a decrease in inhibitoryeffects of metabolic stress induced by KCN (0.3 mM, n=8) DNP (0.8 mM,n=6). However, statistical analysis clearly showed that dantrolene-Na hasa markedly greater effect compared to EGTA on inhibitory effect ofmetabolic stress.In conclusion, a result from this study indicates that Ca++ ion play arole, at least partially, on DNP and KCN induced inhibition of myometrialcontractions of rat. However, this inhibition can be reversed by inhibitionof Ca++-release from intracellular stores and chelation of intracellularcalcium.Key words: myometrium, DNP, EGTA, KCN, Dantrolene-Na, metabolicstress.