LYSOPHOSPHATIDIC ACID, SERUM, AND HYPOSMOLARITY ACTIVATE CL- CURRENTSIN CORNEAL KERATOCYTES

The influence of serum, lysophosphatidic acid (LPA), and hyposmotic st ress on the ion channel activity of normal and cryo-injured rabbit cor neal keratocytes was investigated. Whole cell currents were examined u sing the amphotericin perforated-patch technique. In cells from wounde d corneas, fetal bovine serum activated large, holding voltage-insensi tive, fast-activating, 4,4'-diisothiocyanostilbene-2,2'-disulfo acid ( DIDS)-, flufenamic acid-, and 5-nitro-2-(3-phenylpropylamino)benzoic a cid (NPPB)-blockable outward currents showing inactivation at depolari zed voltages. LPA activated identical currents, also only in cells fro m wounded corneas. Blocker and reversal potential experiments characte rized the current as a Cl-current (I-Cl). Lysophosphatidylcholine (10 mu M) failed to activate the current. An identical current was activat ed by hyposmotic stimulation in cells from control and wounded corneas . Hyposmotic stimulation also activated I-Cl in cells from wounded cor neas that were unresponsive to LPA. We conclude that serum, LPA, and h ypotonic stress activate Ia in keratocytes from wounded corneas. We al so conclude that LPA is a serum factor that can activate I-Cl and that hyposmotic activation may work through a signaling pathway separate f rom that of LPA.