Electrical properties of cultured renal tubular cells (OK) grown in confluent monolayers.

UNLABELLED: OK cells grown to confluent monolayers were investigated by microelectrode techniques and microinjection. Cell membrane potential difference (PDm) in bicarbonate-free solution is -61.8 +/- 0.6 mV (n = 208), cell membrane resistance (Rm) amounts to 1.4 +/- 0.2 k omega. cm2 (n = 8). The apparent transference number for potassium (t'k+) is 71 +/- 3% (n = 28) and can be reduced by 3 mmol/l BaCl2 to 7.5 +/- 4.0%; (n = 8). In the presence of extracellular CO2 and HCO3- (pH 7.4) the cells acidify by 0.34 +/- 0.05 pH units (n = 12). This leads to a depolarization of PDm by 8.4 +/- 1.8 mV (n = 8), an increase in Rm by 49 +/- 10% (n = 10), and a reduction of K+-conductance to 63 +/- 5% (n = 13). Intracellular acidification by the NH4Cl-prepulse technique also inhibits K+-conductance and depolarizes the membrane. Recovery from an intracellular acid load is reflected by cell membrane repolarization. This recovery can be inhibited by amiloride (10(-3) mol/l). Na+- and Cl- -conductances could not be detected. The transepithelial resistance (Rte) of OK cell monolayers 1 day after plating is 41 +/- 6 omega.cm2 and decreases with time after plating. Intercellular communication (electrical or dye coupling) was not observed.
CONCLUSIONS: 1. The membrane potential of OK cells is largely determined by a pH-sensitive, barium-blockable K+-conductance. 2. Amiloride-blockable Na+/H+-exchange is reflected by membrane potential changes via this K+-conductance. 3. Monolayers of OK cells are electrically leaky.