The effect of calcium and calcium antagonists on the electrically-evoked contractile activity of isolated rat ovaries.

The effects of different calcium concentrations and calcium antagonists on the mechanical activity evoked by electrical field stimulation of isolated rat ovaries, were explored. It was observed that the force of contraction augmented and the electrical threshold diminished as the (Ca2+)0 increased. On the other hand, in the presence of calcium antagonists (Verapamil, D-600 and MnCl2) as well as in calcium-free media, the force of contraction decreased and the electrical threshold augmented. TTX, high (K+)0, propranolol and phentolamine failed to modify the responses of rat ovaries to the electrical field stimulation. The results suggest an important participation of calcium ions in the mechanisms of ovarian excitation-contraction coupling. The fast channels and intraovarian nerve endings, do not appear to be relevant for the electrically-evoked contractions of isolated rat ovaries.