Increase in muscarinic stimulation-induced Ca response by adenovirus-mediated Stim1-mKO1 gene transfer to rat submandibular acinar cells in vivo

Adenoviruses have been used for gene transfer to salivary gland cells in vivo. Their use to study the function of salivary acinar cells was limited by a severe inflammatory response and by the destruction of fluid-secreting acinar cells. In the present study, low doses of adenovirus were administered to express Stim1-mKO1 by retrograde ductal injection to submandibular glands. The approach succeeded in increasing muscarinic stimulation-induced Ca²⁺ responses in acinar cells without inflammation or decreased salivary secretions. This increased Ca²⁺ response was notable upon weak muscarinic stimulation and was attributed to increased Ca²⁺ release from internal stores and increased Ca²⁺ entry. The basal Ca²⁺ level was higher in Stim1-mKO1-expressing cells than in mKO1-expressing and non-expressing cells. Exposure of permeabilized submandibular acinar cells, where Ca²⁺ concentration was fixed at 50 nM, to inositol 1,4,5-trisphosphate (IP₃) produced similar effects on the release of Ca²⁺ from stores in Stim1-mKO1-expressing and non-expressing cells. The low toxicity and relative specificity to acinar cells of the mild gene transfer method described herein are particularly useful for studying the molecular functions of salivary acinar cells in vivo, and may be applied to increase salivary secretions in experimental animals and human in future.