Two types of store-oerated Ca²⁺ channels with different activation in rat submandibular acinar cells

Abstract

Store-operated Ca²⁺ channels were stimulated using 4 microM thapsigargin, sarco(end)plasmic reticulum Ca²⁺ ATPase inhibitor, in Ca²⁺-free solution (no added Ca²⁺ + 1mM EGTA) followed by superfusion with control (Ca²⁺-containing) solution. This protocol resulted in a [Ca²⁺]_i increase, which was inhibited in the presence of 100 microM Gd³⁺, 100microM La³⁺ but was unaffected by addition of 1 microM Gd³⁺ or 10 microM H-89, protein kinase A inhibitor. A restoration from a high K+ solution(Ca²⁺-containing) to control solution also evoked an [Ca²⁺]_i increase during thapsigargin stimulation, and an [Ca²⁺]_i increase following reintroduction of Ca²⁺ during thapsigargin stimulation was completely inhibited by addition of 1 microM Gd³⁺ but was partially affected by addition of 10 microM H-89 . Thus, one effect of the reintroduction of Ca²⁺ is likely to be a hyperpolarized pulse. In conclusion, rat submandibular acinar cells have at least two types of Ca²⁺ channels; one is activated by the store-depletion in Ca²⁺-free solution, and the other is by the store-depletion with a hyperpolarized pulse. [Jpn J Physiol 55 Suppl:S130 (2005)]