Action of ouabain on the contraction of ileal longitudinal muscle by manganese ions in a Ca(2+)-free, high-K(+), Na(+)-sufficient or Na(+)-deficient solution

Abstract

The action of ouabain, an external Na(+)-dependent inhibitor of active glucose transport, on the contraction by Mn(2+)in a Ca(2+)-free, Na(+)-sufficient or Na(+)-deficient medium was examined in ileal muscle. Ouabain ( 9 x 10(-5)m) inhibited the contraction by 5 mm Mn(2+)in a Ca(2+)-free, 60 mm K(+), Na(+)-sufficient medium in ileal muscle. The addition of pyruvate or lactate, utilized independently in the external Na(+)in the pretreatment with ouabain, induced the dose-dependent contraction and manganese uptake by Mn(2+)in the Ca(2+)-free, 60 mm K(+), Na(+)-sufficient medium. These results suggest that Mn(2+)-induced ileal contraction in a high-K(+), Na(+)-sufficient medium is maintained by an active glucose transport, dependent on external Na(+). While, in contrast, Mn(2+)-induced contraction in a high-K(+), Na(+)-deficient medium is maintained by an external Na(+)-independent glucose transport, and is insensitive to ouabain.