Glucose-6-phosphate dehydrogenase and glutathione reductase support antioxidant enzymes in nerves and muscles of rats during nerve regeneration

The effects of the rat sciatic nerve crush on the activities of glucose-6-phosphate dehydrogenase (G6PD), glutathione reductase (GR), glutathione peroxidase (GPX), superoxide dismutase (SOD) and catalase (CAT) were examined in regenerating nerve and in two reinnervating muscles: the slow twitch soleus and the fast twitch extensor digitorum longus (edl). The enzyme activities in the crushed side, were compared with the contralateral homologue tissues and basal values, determined in uncrushed animals. In the crushed side, the activity of G6PD, GR, GPX and CAT of the sciatic nerve and both muscles markedly increased in comparison with the uncrushed side. In the nerve and in both muscles, SOD activity decreased at 13 days, then rose to values higher than normal, but the pattern of the crushed side was not significantly different from that of the uncrushed. In the uncrushed side, we observed a significant increase of nerve G6PD, GPX and CAT activities compared to basal values, while in both muscles, values fluctuated around the normal without any significant variation. The mechanism of these enzymatic changes is unknown, however our work suggests that: (i) during nerve regeneration, an oxidative stress occurs in nerve and muscle, which causes adaptive responses in antioxidant enzymes; (ii) the maximum antioxidant power is expressed during the period of synaptic retraction; (iii) G6PD and GR activities are synergistically modulated with GPX and CAT, while SOD activity appears independently regulated.