Intracellular Ca(2+) changes induced by in vitro ischemia in rat retinal slices.
The effect of ischemia on intracellular Ca(2+)concentration [[Ca(2+)](i)] in retinal slices was investigated. [Ca(2+)](i)in each layer of the retina was determined from fluorescence images in rat retinal slices loaded with fura2-AM. Ischemic like conditions were imposed on the retinal slice in vitro by perfusion with an oxygen/glucose deprived solution. All measurements were taken at 25 degrees C except when temperature dependence was examined. In response to 100 m M K(+)or 0.2 m M glutamate under normoxic conditions, the [Ca(2+)](i)increase was higher in the inner retinal layers. Fifteen min ischemia evoked an increase in Ca(2+)levels in all layers of the retina, and the rates of increase were especially high in the outer/inner segment layer and the outer nuclear layer. Ischemia in the absence of extracellular Ca(2+)also induced a Ca(2+)rise, but at lower rates than with standard ischemia. Intermittent ischemia, composed of three 15 min bursts of ischemia at 10 min intervals, promoted the Ca(2+)rise. There was a more marked rise in [Ca(2+)](i)when the temperature was increased to 29 or 33 degrees C. Thus, in the rat retinal slice, in vitro ischemia evoked a more marked Ca(2+)rise in the outer retina, which was in contrast to the Ca(2+)responses to glutamate or high K(+). The rates of increase in [Ca(2+)](i)with ischemia were larger at higher temperatures, and intermittent ischemia also promoted the Ca(2+)rise. These increases appear to be derived from predominant influx of extracellular Ca(2+)rather than release of intracellular Ca(2+)stores.
Kuriyama
H
H
Research Laboratory, Senju Pharmaceutical Co. Ltd, Hyogo 651-2241, Japan.
Nakagawa
M
M
Tsuda
M
M
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D005260:Female; D016257:Fura-2 / Q000494:pharmacology; D018698:Glutamic Acid / Q000494:pharmacology; D007511:Ischemia / Q000378:metabolism*; D008297:Male; D008856:Microscopy, Fluorescence; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D012160:Retina / Q000378:metabolism*; D013696:Temperature
D018698:Glutamic Acid; D011188:Potassium; D002118:Calcium; D016257:Fura-2