Abstract
Using glycerinated taenia coli of the guinea-pig, the effects of divalent ions (Ca, Mg, Mn and Zn) on the contractile system of the smooth muscle were studied.
Mg ion is essential for ATP contraction of glycerinated smooth muscle. Mn ion can substitute perfectly for Mg ion, but Ca ion cannot. The initiation of ATP-contraction in the presence of Mn ion is suppressed by addition of higher concentra-tion of Ca ion. Zn depresses the initiation of ATP-contraction, but it is ineffective in relaxing the ATP-contraction.
The present results imply that Zn ion depresses the initiation of contraction by blocking all stages of contractile process in the smooth muscle.
