Mechanosensitive Ca²⁺ channels receive mechanical stimuli in Chara corallina.

Abstract

When Characese cytoplasm is rapidly hydrated, Ca²⁺ is released from some intracellular stores. This is explained as a Ca²⁺ channel activation at the store membrane in a mechanosensitive manner. It may be expected that mechanosensitive Ca²⁺ channels function not only at the membrane of the stores but also other membrane system such as plasma membrane.
According to Shimmen, mechanical stimuli to an intact cell induces receptor potential which reflects activation of Cl^- channels at the plasma membrane. We studied possible contribution of mechanosensitive Ca²⁺ channels on the receptor potential.
Removal of Ca²⁺ in the bathing medium reversibly inhibits the receptor potential. Mechanical stimuli caused not only receptor potential but also increases in cytoplasmic level ofCa²⁺, and both of those amplitudes are dependent on that of mechanical stimulus. These results strongly suggest that mechanical stimulus is first received by mechanosensitive Ca²⁺ channels at the plasma membrane.