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Characterization of voltage-gated, whole-cell ionic currents from conjunctival epithelial cells
1Department of Physiology and Biophysics, University of Tennessee, Memphis 38163, USA.
Purpose:
These studies were performed to characterize the voltage-gated, 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 dissociated 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 cation current. A second nonselective cation current also appeared to be present. The inward current was observed in a KCl Ringer's bath and was almost nonexistent in a NaCl bath. The current was Ba(2+)- and Cs(+)-sensitive. The second K+ current became saturated at depolarized voltages and was Ba(2+)- and quinidine-sensitive. The first outward nonselective cation current was typically less than 100 pA in amplitude and activated 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'-disulfonic acid or 5-nitro-2-(3-phenylpropylamino)benzoic acid. The second nonselective cation current was larger and Gd(3+)-insensitive. The primary current observed in goblet cells was a large outward K+ current.
Conclusions:
The primary currents observed during whole-cell patch clamping of bulbar conjunctival epithelium are a Ba(2+)- and Cs(+)-sensitive, inwardly rectifying K+ current, a saturating K+ current, and two outwardly rectifying nonselective cation currents. Goblet cells contain a large outward K+ current.