Modification of the mechanical response of the smooth muscles of pregnant mouse myometrium and guinea pig ileum by cadmium and manganese ions.

Abstract

Effects of divalent cations on pregnant mouse myometrium and guinea pig ileum were investigated by recording electrical and mechanical activities.1. Application of transition metal cations (Mn, Cd, Co, Ni, and Zn) inhibited the spontaneous activities of mouse myometrium. Except for Mn, treatment with these cations in a concentration of 1mM and for 1-2min caused an irreversible suppression of the mechanical response.2. Myometrial membrane was hyperpolarized with 0.5mM Cd decreasing membrane resistance. During application, contractures induced by excess K or carbachol was inhibited. After treatment with 0.5-1mM Cd for 1-2min, electrical and mechanical activities dissociated, i. e. spike activity resumed but mechanical activity was suppressed. The membrane was depolarized by carbachol to the control value, but contraction did not developed.3. By contrast, contracture of mouse myometrium induced by excess K or carbachol application were potentiated after treatment with Mn.4. The effects of divalent cations on guinea pig ileum were essentially the same as with mouse myometrium, i. e. treatment with Mn potentiated mechanical response whereas other ions caused irreversible suppression.