Keller S K, Jentsch T J, Koch M, Wiederholt M
Am J Physiol. 1986 Jan;250(1 Pt 1):C124-37. doi: 10.1152/ajpcell.1986.250.1.C124.
Passive ion transport properties were studied in confluent monolayers of cultured bovine retinal pigment epithelial cells using intracellular microelectrode technique. The mean stable intracellular (designated by subscript i) potential was -59.1 +/- 0.8 (SE) mV. Extracellular (designated by subscript o) acidification induced a depolarization, whereas alkalinization induced a hyperpolarization. These effects were observed both in bicarbonate-free as well as in HCO3- Ringer (pHo changed by varying [HCO3-]o at constant pCO2). Acidification of pHi (changed by addition and removal of butyrate, CO2 or NH3) also caused a depolarization. Complete removal of HCO3-/CO2 at constant pHo caused a hyperpolarization. K+ transference, checked by applying high K+o, increased with K+o. It decreased with both extra and intracellular acidification and increased with alkalinization. In the presence of Ba2+, voltage reactions to changes in either pHo or pHi were greatly reduced. Depolarization by 40 mM K+ caused a similar reduction. It is suggested that K+ conductance of bovine retinal pigment epithelial cells is reduced by either intra- or extracellular acidification at normal [K+]o. Depolarization by high K+ induces an increase in K+ transference and reduces pH sensitivity.
