Effect of hypotonic media on the membrane voltage of cultured bovine corneal endothelial cells.

The effects of hypotonicity on cultured bovine corneal endothelial cells were investigated using standard microelectrode and superfusion techniques. Confluent monolayers of cells were superfused with an isotonic (305 +/- 5 mosm/kg) control solution until a stable membrane voltage (V) was obtained, then with a hypotonic (240 +/- 5 mosm/kg) solution. Under control conditions, V was - 51.4 +/- 0.8 mV (means +/- SEM, n = 154). Decreasing solution osmolality resulted in an immediate depolarization: mean maximal delta V = 18.7 +/- 0.9 mV at 2.6 +/- 0.2 minutes with a gradual recovery to a new but still depolarized steady-state V (delta v = 11.1 +/- 0.9 mV at 8.2 +/- 0.3 minutes, n = 25). The depolarizing response to hypotonicity persisted in the presence of amiloride (10(-3)M), DIDS (10(-3)M), bumetanide (10(-4)M) or ouabain (10(-4)M) as well as in the absence of extracellular Cl-, Na+, HCO3- or Ca2+. Relative K+ conductance was estimated by the effect on V of increased extracellular [K+] - this was significantly reduced at 5, 10 and 20 mM K+ under hypotonic conditions. The depolarization induced by 1mM Ba2+ was also reduced from 19.6 +/- 0.5 mV (n = 8) under isotonic conditions to 15.4 +/- 0.4 mV (n = 6) under hypotonic conditions (p less than 0.001). The conductive HCO3- pathway - as judged by the hyperpolarization of V induced by increasing extracellular [HCO3-] from 28 to 60 mM, was also reduced under hypotonic conditions (delta V = 17.2 +/- 0.8 mV, n = 13 (isotonic) compared to delta V = 9.5 +/- 0.3 mV, n = 15 (hypotonic].(ABSTRACT TRUNCATED AT 250 WORDS)