Buffer dependence of retinal glycolysis and ERG potentials.

Using the isolated rat retina, the present experiments have examined the effects of varying the type and concentration of buffer system with and without changes in external pH on lactic acid production and ERG potentials. The buffers chosen for study included bicarbonate/CO2, HEPES, Tris+ and phosphate. High rates of retinal glycolysis were observed with either 25 mM bicarbonate and 5% CO2 (control condition) or with 30 mM quantities of the other buffers at an external pH of 7.4. Significantly lower rates of retinal glycolysis were obtained when the concentration of each buffer was reduced to 10, 5 or 3 mM without a change in external pH. Lactic acid production was also decreased when the external pH was lowered regardless of the buffer system employed. The a- and b-waves were well maintained in the presence of 25 mM bicarbonate and 5% CO2. Lowering the bicarbonate concentration at constant external pH led to a decrease in their amplitudes. With either Hepes, Tris+ or phosphate employed at concentrations between 3 and 30 mM the amplitude of the a-wave was reduced and the b-wave was lost. These results show that the nature and concentration of the buffer system used in in vitro retinal studies influences metabolic and electrical activities in this tissue and emphasize the importance of the buffer as a constituent of the incubation medium.