Abstract

Mn²⁺, at 5 mM, induced a large tension development in isotonic 126 mM K⁺ medium in taenia coli of guinea-pig, although Na⁺ was not contained in the external medium. Trifluoperazine and W-7, a calmodulin inhibitor, and wortmannin, a myosin light chain kinase inhibitor, inhibited dose-dependently both the contraction by 5 mM Mn²⁺ in hypertonic 60 mM K⁺, Na⁺-sufficient medium and in isotonic 126 mM K⁺, Na⁺-deficient medium. This indicates that the primary target of a rise in intracellular Mn²⁺ through voltage-dependent Ca²⁺ channels during membrane depolarization with K⁺ is thought to be calmodulin. Thereafter, Mn bound to calmodulin might activate myosin light chain kinase for the initiation of force production in ileal muscle.

Author Details

Authors

• Y. Asanuma
• T. Nasu

Departments

• Department of Veterinary Pharmacology, Faculty of Agriculture, Yamaguchi University, Japan

Address

Prof. T. Nasu
Department of Veterinary Pharmacology
Faculty of Agriculture
Yamaguchi University
Yamaguchi 753, Japan
Email: [email protected]

Citation