PI(CLN) CAN REGULATE SWELLING-INDUCED CL- CURRENTS IN EITHER LAYER OFRABBIT CILIARY EPITHELIUM

Swelling-induced Cl- currents were investigated in freshly prepared no n-pigmented epithelial (NPE) and pigmented epithelial (PE) cells of th e rabbit ciliary body using the whole-cell patch clamp technique. Expo sure of both NPE and PE cells to hypotonic stress induced Cl- currents that exhibited outward rectification and were insensitive to Ca+2. We found that swelling-induced Cl- currents in PE cell are observed shor tly after isolation. The swelling-induced Cl- current showed little or no inactivation at positive membrane voltages and was sensitive to 10 0 mu M NPPB and 100 mu M DIDS. Injection of cRNA encoded rabbit pI(Cln ) into Xenopus oocytes produced an outwardly rectifying: Cl- current d isplaying features consistent with the swelling-induced Cl- current in epithelium. pI(Cln) is ubiquitous in the ciliary epithelium. It parti cipates in the equilibration of short term tonicity alterations, a phe nomenon underlying mechanisms with larger and slower amplitudes for aq ueous secretion by these cells. (C) 1998 Academic Press.