Studies on the eye lens in poikilothermal animals. II. Stimulation of anaerobic glycolysis in rainbow trout lenses incubated with Ca 2+-free medium

Abstract

The effects of Ca 2+-free medium on cation levels and lactic acid production of rainbow trout lens incubated at various temperatures were examined in order to study passive cation transport system. Na +-K + ratio (Na +/K +) increased when the lens was treated with Ca 2+-free medium, but the effect of Ca 2+-free medium was lowest between 15 and 20°C which was the optimum water temperature for rainbow trout. Lactic acid production was stimulated between 15 and 20°C in Ca 2+-free medium. It was also stimulated at 37°C in rat lenses incubated with Ca 2+-free medium. However, the production was suppressed in ouabain-treated rainbow trout lenses. The suppression of Na +/K + increase between 15 and 20°C disappeared when the lens was treated with both Ca 2+-free medium and ouabain. These results suggest that Na,K-ATPase activity and glycolysis were stimulated to prevent the increase of Na +/K + in Ca 2+-free medium. In addition, these results indicate that the optimum temperature was between 10 and 20°C for the rainbow trout lens incubation in vitro, which is also the optimum water temperature in vivo.