Properties of an anion/H+ cotransport system in L1210 cells that utilizes phthalate as a nonphysiological substrate

[14C]Phthalate is transported into L1210 cells via two separate routes, an anion exchange system whose primary substrates are folate compounds, and a second less active system which is sensitive to bromosulfophthalein. When the principal uptake component was blocked by a specific irreversible inhibitor of this system, the remaining route (at pH 7.4) appeared to be saturable and was inhibited by several anions in addition to bromosulfophthalein (Ki = 2 microM), including 8-anilino-1-naphthalein sulfonate (Ki = 25 microM), unlabeled phthalate (Ki = 500 microM), and chloride (Ki = 3500 microM). A pronounced effect by pH was also observed. Influx and total uptake of phthalate both increased progressively with decreasing pH and reached values that were 20-fold higher at pH 6.0, compared with pH 7.4. This pH-dependent increase could be blocked, however, by the addition of compounds (nigericin and carbonylcyanide m-chlorophenylhydrazone) which, in combination, collapse proton gradients. Phthalate efflux was relatively insensitive to changes in extracellular pH but could be inhibited (up to 90%) by bromosulfophthalein. Several other anions also inhibited efflux, but to a lesser extent, while chloride, phthalate, lactate, glycolate and acetate enhanced efflux up to 1.8-fold. Efflux also increased at pH 6.0, but not at pH 7.5, upon addition of nigericin and carbonylcyanide m-chlorophenylhydrazone. These results suggest that phthalate is a nonphysiological substrate for a carrier system which mediates transport via an anion/H+ symport mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)