Involvement of sodium/calcium exchange in the diclofenac-induced spasmolytic effect on rat uterus

1. The effect of diclofenac (10-100 microM) on rat uterus contraction and its modification by ouabain (0.1 mM), amiloride (0.1 and 1 mM), ouabain (0.1 mM) plus amiloride (1 mM) and the replacement of sodium by choline have been assayed. 2. Diclofenac produces dose-dependent relaxation of vanadate (0.3 mM)-induced contraction (EC50, 17.3 +/- 1.8 microM). This effect is significantly reduced in choline medium (EC50, 49.1 +/- 4.5 microM) and by ouabain in sodium-medium (EC50, 52 +/- 7 microM). 3. Amiloride displaces, in a dose-dependent way, the diclofenac-induced relaxant effect. However, ouabain plus amiloride did not produce a sinergic effect. 4. Our results suggest that diclofenac produces relaxation of vanadate-induced contraction by activation of Na+/Ca(2+)-exchange.