Sodium bicarbonate cotransport in cultured pigmented ciliary epithelial cells

Abstract

Uptake of ²²Na⁺ was studied in cultured bovine pigmented ciliary epithelial cells (PE) in HCO₃-containing media. Two components of Na⁺-uptake were stimulated by intracellular acidification (NH₄⁺-prepulse): One was amiloride-sensitive, the other DIDS-sensitive. The amiloride-sensitive component of Na⁺-uptake probably represents Na⁺/H⁺-exchange, which has previously been characterized in PE. The second, DIDS-sensitive component stimulated by intracellular acidification, was C1⁻ and HCO₃⁻-dependent. We conclude that a stilbene-sensitive, C1⁻-dependent Na⁺-HCO₃⁻-cotransport is present in PE. This transport could play an important role in aqueous humor formation.