Glutathione depletion causes an uncoupling effect on retinal horizontal cells through oxidative stress

To investigate a physiological role of glutathione in the horizontal cells of carp retina, the gap junctional intercellular communication between hori zontal cells was studied using the techniques of intracellular recording of light-induced responses and coupling of the fluorescence dye Lucifer Yello w. Intravitreal injection of 2.5 mu mol L-buthionine sulfoximine, an inhibi tor of glutathione synthesis, induced a dramatic reduction (20% of control) of retinal glutathione level two days after treatment. The low level of gl utathione continued for a further four to five days, and thereafter gradual ly recovered to about 40% (20 days after injection) and 70% (50 days after injection) of the control level. The spatial properties of the photopic L-t ype horizontal cell response were examined by enlarging the diameter of the central spot and peripheral annulus over the recording point. In normal re tinas, the response amplitude of horizontal cells was monotonically enhance d as the diameter of the spot increased (0.5-4.0 mm) and correspondingly th e dye diffusion area was wide, as the injected Lucifer Yellow normally diff used to several neighboring cells. Treatment with L-buthionine sulfoximine significantly altered the spatial properties of horizontal cells by increas ing the response amplitude to central spots and slightly decreasing that to peripheral annuli, which were observed by four days after injection. It al so restricted intracellular Lucifer Yellow to one or two cells. Accompanyin g the recovery of the cellular level of glutathione, the spatial properties and dye coupling of horizontal cells were restored to normal. A time lag (two days) of initiation in retinal glutathione depletion and al teration of spatial or dye coupling properties of horizontal cells is discu ssed, together with reactive oxygen species accumulation. (C) 1999 IBRO. Pu blished by Elsevier Science Ltd.