The inhibitory action of zinc sulphate on the contractile activity of guinea-pig ileum.

The present study examines the inhibitory action of zinc sulphate (ZnSO4) on the contractile response of various agonists on guinea-pig isolated ileum. Different doses of agonists were selected to produce similar contractile activity, in order to compare the degree of inhibition produced by ZnSO4. Preincubation of ileum with ZnSO4 1 x 10(-3) or 3 x 10(-3) M for 10 min dose-dependently and significantly prevented the contraction induced by acetylcholine (1.7 x 10(-8) M), 5-HT (2.4 x 10(-6) M), histamine (5.4 x 10(-7) M) and nicotine (1.7 x 10(-6) M) but not by prostaglandin E2 (PGE2, 8.5 x 10(-9) M). The same doses of ZnSO4 reduced the twitch contraction produced by electrical field stimulation. These findings indicate that the contractile activity of PGE2 is mediated by a mechanism different from that of other agonists and of electrical field stimulation. It is likely that the contractile activity of PGE2 is acting through the receptors on the ileal muscle which are not blocked by ZnSO4 pretreatment.