The primary culture of marginal cells from the explant of the stria vascularis of guinea-pigs was established and confirmed by morphological, immunohistochemical and physiological characters of the cultivated cells. The positive stain of cytokeratin 18 without vimentin and desmin expressions indicated the epithelial origin of the cultured polygonal cells. Electron microscopical findings of cultured cells resembled the morphological characteristics of marginal cells. The addition of 100 μM ouabain to the cultured cells significantly increased the intracellular Na + concentration, providing the evidence for the presence of Na + pump. Using the cultured marginal cells identified by the above-mentioned findings, the effects of neurotransmitters and hormones in regulating intracellular Ca 2 + concentration ([Ca 2 + ] i ) were investigated. The addition of 10 - 4 M ATP caused an increase in [Ca 2 + ] i , which was independent of the presence of extracelluar Ca 2 + . The rank order of agonist potency was ATP > α,β-methylene ATP > ADP. Adenosine, however, evoked no response. Cultured marginal cells may possess P 2 -purinergic receptors which mobilize Ca 2 + from the intracellular Ca 2 + pool. [Marginal cell, Cell culture,Na + + ATPase, Intracellular Ca 2 + concentration, ATP]