Ion Transport In An Immortalized Rat Submandibular Cell Line Smg-C6 (44550)

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 (l_sc) 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 l_sc, followed by a sustained decreased below baseline value. The peak Δl_sc, 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 l_sc was sensitive to apical Na⁺ replacement or amiioride (half-maximal inhibitory concentration 392 nM). Following pretreatment with amiloride, ATP induced a significantly greater l_sc; however, the post-stimulatory decline was abolished, suggesting an ATP-induced Inhibition of amllo-ride-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 l_sc accounted for by amiloride-sensitive Na⁺ absorption.