CHARACTERIZATION OF VOLTAGE-GATED, WHOLE-CELL IONIC CURRENTS FROM CONJUNCTIVAL EPITHELIAL-CELLS

PURPOSE. These studies were performed to characterize the voltage-gate d, whole-cell ionic currents in rabbit bulbar conjunctival epithelial and goblet cells. METHODS. New Zealand White rabbits were killed, and the bulbar conjunctiva was isolated. Conjunctival cells were dissociat ed for patch clamp analysis of whole-cell currents. The amphotericin, perforated-patch, whole-cell technique was used. RESULTS. Conjunctival epithelial cells had a mean capacitance of 6.72 pF (SE = 0.49; n = 25 ). The primary currents found were an inwardly rectifying K+ current, a saturating K+ current, and an outwardly rectifying nonselective cati on current. A second nonselective cation current also appeared to be p resent. The inward current was observed in a KCl Ringer's bath and was almost nonexistent in a NaCl bath. The current was Ba2+- and Cs+-sens itive. The second K+ current became saturated at depolarized voltages and was Ba2+- and quinidine-sensitive. The first outward nonselective cation current was typically less than 100 pA in amplitude and activat ed at voltages positive to 0 mV. Tail current experiments showed that the current was cation selective. The current was blocked by Gd3+ but not by the Cl- current blockers 4,4'-diisothiocyanostilbene-2,2'-disul fonic acid or 5-nitro-2-(3-phenylpropylamino)benzoic acid. The second nonselective cation current was larger and Gd3+-insensitive. The prima ry current observed in goblet cells was a large outward K+ current. CO NCLUSIONS. The primary currents observed during whole-cell patch clamp ing of bulbar conjunctival epithelium are a Ba2+- and Cs+-sensitive, i nwardly rectifying K+ current, a saturating K+ current, and two outwar dly rectifying nonselective cation currents. Goblet cells contain a la rge outward K+ current.