動物細胞における膜電位・細胞内Ca²⁺振動

抄録

A variety of nammalian cells exhibit membrane potential oscillations composed of repeated hyperpolarizations. Such hyperpolarizing oscillations are usually caused by cyclic increases in the cytosolic Ca²⁺ ions, which in turn, periodically stimulate Ca²⁺-activated K⁺ channels. Intracellular Ca²⁺ oscillations could be brought about by a feedback relationship between an autocatalytic Ca²⁺ input and a delayed Ca²⁺ output. In mouse fibroblastic L cells, the operation of Ca²⁺ channels and that of Ca²⁺ pump are involved in the oscillations. The Ca²⁺ channels are activated by stimulation of membrane receptors to complement components (such as Clq) and nucleotides (such as ATP), which are chemotactic factors for the firboblasts. In human epithelial Intestine 407 cells, stimulation of receptors to intestinal secretagogues (such as acetylcholine, histamine, serotonin and VlP) gives rise to Ca²⁺ release from some intracellular calcium stores. Under appropriate conditions, receptor stimulation by agonists was found to lead to generation of the oscillations in both cell species. Thus, it is strongly suggested that oscillations of membrane potential and cytosolic Ca²⁺ occur in the recepor-activated fibroblasts and enterocytes in vivo, and that the oscillations play an important role in Ca²⁺-mediated cell activities such as fibroblast chemotaxis and intestinal secretion.