GLUCOSE AVAILABILITY ALTERS ISCHEMIA-INDUCED CHANGES IN INTRACELLULARPH AND CALCIUM OF ISOLATED RAT SPINAL ROOTS

Peripheral nerves in diabetic patients shaw an enhanced liability to i schaemic lesions. Using an in vitro model, we have now analysed the po ssible role of intracellular proton (pH(i)) and calcium concentrations ([Ca2+](i)) for the pathophysiology of this phenomenon. isolated rat spinal toots were preincubated for 3 to 6 h in either 5 or 25 mM of D- glucose before transient exposure to gaseous hypoxia or cyanide. Intra cellular pH and Ca2+ concentrations were measured photometrically by m eans of the fluorescent dyes carboxy-SNARF-1 and a combination of Calc ium Green-1 and Fura Red, respectively. The following observations wer e made. (a) The presence of 25 mM D-glucose resulted in stronger intra cellular acidification and much slower post-hypoxic recovery of pH(i) as compared to 5 mM D-glucose. (b) Intracellular calcium increased dur ing hypoxia and recovered quickly on reoxygenation. There were no stat istically significant signals in either high or normal concentrations of D-glucose, although on average less rise was seen in high glucose. (c) Inhibition of glycolysis with iodoacetate reduced the acidificatio n but amplified the rise in [Ca2+](i) seen during transient hypoxia. T hese data suggest that hypoxia-induced nerve acidification rather than a rise in [Ca2+](i) might contribute to ischaemic lesions found in di abetic neuropathy.