Calcium requirement of uterine contraction induced by PGE1: Importance of intracellular calcium stores |
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Authors: | A Villar MP D'Ocon E Anselmi |
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Institution: | Departamento de Farmacognosia y Farmacodinamia Faculted de Farmacia. Avad. Blasco Ibáñez, 13 46010 Valencia. Spain |
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Abstract: | The contraction of the rat uterus in response to PGE1 in high K+ medium and in Ca-free solution which contained EDTA has been investigated in order to examine whether excitation-contraction coupling involves the release of Ca from an intracellular store.In uterus maximally contracted by K+, cumulative concentrations of PGE1 (1.25 – 20 ng/ml) caused maintained concentration-dependent contraction. PGE1 induced sustained contraction of rat uterus in Ca-free medium after incubation with 3mM EDTA for 50 min. In these conditions the involvement of extracellular Ca is highly unlikely. The PGE1-induced contraction could be repeated without exposure to external Ca ions and with only slight reduction in magnitude. The PGE1 concentrations required to elicit uterine contraction in Ca-free solution were about 1000 times higher than the effective doses in KCl-depolarized uterus.In conclusion, the present investigation shows that Ca influx is not essential for PGE1-induced contraction of rat uterus, although extracellular Ca enhances it presumably by increasing the free Ca levels in the cytosol. |
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