Expression of I_sK Protein mRNA in Cultured Rat Strial Marginal Cells

Abstract

A cell culture system of marginal cells (MC) of the rat stria vascularis was established by the explant method. When grown on plastic dishes, cultured MC showed a polygonal ?cobblestone-like? appearance. Dome formation, composed of several hundreds to thousands of cells, occurring after confluence suggested that vectorial transport of ion(s) with accompanying fluid developed in the cultured MC. Transmission electron microscopy demonstrated junctional complexes formed of tight junctions and desmosomes at the upper lateral membranes. The polymerase chain reaction (PCR) product, amplified with primers made from the cDNA reverse transcribed from cultured MC, yielded a distinct band compatible with the expected size of the PCR products amplified from cDNA of positive control groups containing I_sK protein, indicating that cultured MC expressed the I_sK protein mRNA. The results show that cultured MC can form large domes and express the most characteristic I_sK protein, indicating that they maintain their vectorial electrolyte transport function and, possibly, the ability to secrete K⁺ in this condition.