ATP-induced increase in intracellular Ca2+ concentration in the cultured marginal cell of the stria vascularis of guinea-pigs.

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 microM 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 Ca2+ concentration ([Ca2+]i) were investigated. The addition of 10(-4) M ATP caused an increase in [Ca2+]i, which was independent of the presence of extracellular Ca2+. The rank order of agonist potency was ATP > alpha, beta-methylene ATP > ADP. Adenosine, however, evoked no response. Cultured marginal cells may possess P2-purinergic receptors which mobilize Ca2+ from the intracellular Ca2+ pool.