Ion transport in an immortalized rat submandibular cell line SMG-C6

The immortalized rat submandibular epithelial cell line, SMG-C6, cultured o n porous tissue culture supports, forms polarized, tight-junction epithelia facilitating bioelectric characterization in Ussing chambers. The SMG-C6 e pithelia generated transepithelial resistances of 956+/-84 Ohm.cm(2) and po tential differences (PD) of -16.9+/-1.5mV (apical surface negative) with a basal short-circuit current (I-SC) of 23.9 +/- 1.7 mu A/cm(2) (n = 69), P2 nucleotide receptor agonists, ATP or UTP, applied apically or basolaterally induced a transient increase in I,,, followed by a sustained decreased bel ow baseline value, The peak Delta/(SC) increase was partly sensitive to CI- and K+ channel inhibitors, DPC, glibenclamide, and tetraethylammonium (TEA ) and was completely abolished following Ca2+ chelation with BAPTA or bilat eral substitution of gluconate for CI-. The major component of basal I-SC w as sensitive to apical Na+ replacement or amiloride (half-maximal inhibitor y concentration 392 nM), Following pretreatment with amiloride, ATP induced a significantly greater I-SC; however, the poststimulatory decline was abo lished, suggesting an ATP-induced inhibition of amiloride-sensitive Na+ tra nsport. Consistent with the ion transport properties found in Ussing chambe rs, SMG-C6 cells express the rat epithelial Na+ channel alpha-subunit (alph a-rENaC). Thus, cultured SMG-C6 cells produce tight polarized epithelia on permeable support with stimulated CI- secretory conductance and an inward I -SC accounted for by amiloride-sensitive Na+ absorption.