Ion Transport in an Immortalized Rat Submandibular Cell Line SMG‐C6

Abstract

Abstract. The immortalized rat submandibular epithelial cell line, SMG‐C6, cultured on porous tissue culture supports, forms polarized, tight‐junction epithelia facilitating bioelectric characterization in Ussing chambers. The SMG‐C6 epithelia generated transepithelial resistances of 956±84Ω.cm2 and potential differences (PD) of −16.9 ± 1.5mV (apical surface negative) with a basal short‐circuit current (Isc) of 23.9 ± 1.7 μA/cm2 (n = 69). P2 nucleotide receptor agonists, ATP or UTP, applied apically or basolaterally induced a transient increase in Isc, followed by a sustained decreased below baseline value. The peak ΔIsc increase was partly sensitive to Cl− and K+ channel inhibitors, DPC, glibenclamide, and tetraethylammonium (TEA) and was completely abolished following Ca2+ chelation with BAPTA or bilateral substitution of gluconate for Cl−. The major component of basal Isc was sensitive to apical Na+ replacement or amiloride (half‐maximal inhibitory concentration 392 nM). Following pretreatment with amiloride, ATP induced a significantly greater Isc; however, the poststimulatory decline was abolished, suggesting an ATP‐induced inhibition of amiloride‐sensitive Na+ transport. Consistent with the ion transport properties found in Ussing chambers, SMG‐C6 cells express the rat epithelial Na+ channel α‐subunit (α‐rENaC). Thus, cultured SMG‐C6 cells produce tight polarized epithelia on permeable support with stimulated Cl− secretory conductance and an inward Isc accounted for by amiloride‐sensitive Na+ absorption.