Mechanics of manganese ions-induced contraction of ileal longitudinal muscle in Ca 2+-free, high-K + medium

Abstract

1. 1. Mn 2+ (5 mM) evoked the contraction of ileal longitudinal muscle in a Ca 2+-free, high-K +(60 mM) medium. Metabolic inhibitors, such as iodoacetic acid or glucose removal, reduced the contraction by Mn 2+ in the Ca 2+-free, high-K + medium, suggesting that the contraction by Mn 2+ depends on energy metabolism. 2. 2. By the abrupt decrease in length of the ileum during contraction 3 hr after the addition of 5 mM Mn 2+ in Ca 2+-free, high-K + medium, a rapid decrease in tension was seen, and redevelopment of tension followed, which is indicative of an active state. 3. 3. In the late phase, 5 hr after the Mn 2+-induced contraction, a similar decrease in the length also caused a rapid decrease in tension, without however, a redevelopment of tension. This probably indicates that the myofilaments in this phase transferred to a state of static interaction.