INVOLVEMENT OF SODIUM-CALCIUM EXCHANGE IN THE DICLOFENAC-INDUCED SPASMOLYTIC EFFECT ON RAT UTERUS

1. The effect of diclofenac (10-100 mu M) on rat uterus contraction an d its modification by ouabain (0.1mM), amiloride (0.1 and 1mM), ouabai n (0.1mM) plus amiloride (1mM) and the replacement of sodium by cholin e have been assayed. 2. Diclofenac produces dose-dependent relaxation of vanadate (0.3 mM)-induced contraction (EC(50), 17.3 +/- 1.8 mu M). This effect is significantly reduced in choline medium (EC(50), 49.1 /- 4.5 mu M) and by ouabain in sodium-medium (EC(50), 52 +/- 7 mu M). 3. Amiloride displaces, in a dose-dependent way, the diclofenac-induce d relaxant effect. However, ouabain plus amiloride did not produce a s inergic effect. 4. Our results suggest that diclofenac produces relaxa tion of vanadate-induced contraction by activation of Na+/Ca2+-exchang e.