Action of ouabain on the contraction of ileal longitudinal muscle by manganese ions in a Ca2+-free, high-K+, Na+-sufficient or Na+-deficient solution

The action of ouabain, an external Na+-dependent inhibitor of active glucos e transport, on the contraction by Mn2+ in a Ca2+-free, Na+-sufficient or N a+-deficient medium was examined in ileal muscle. Ouabain (9 x 10(-5) M) in hibited the contraction by 5 mM Mn2+ in a Ca2+-free, 60 mM K+ Na+-sufficien t medium in ileal muscle. The addition of pyruvate or lactate, utilized ind ependently in the external Nai in the pretreatment with ouabain, induced th e dose-dependent contraction and manganese uptake by Mn2+ in the Ca2+-free, 60 mM K+, Na+-sufficient medium. These results suggest that Mn2+-induced i leal contraction in a high-K+, Na+-sufficient medium is maintained by an ac tive glucose transport, dependent on external Na+. While, in contrast, Mn2-induced contraction in a high-K+, Na+-deficient medium is maintained by an external Na+-independent glucose transport, and is insensitive to ouabain. (C) 2000 Academic Press.