Apparent Km of mitochondria for oxygen computed from Vmax measured in permeabilized muscle fibers is lower in water enriched in oxygen by electrolysis than injection

BACKGROUND: It has been suggested that oxygen (O(2)) diffusion could be favored in water enriched in O(2) by a new electrolytic process because of O(2) trapping in water superstructures (clathrates), which could reduce the local pressure/content relationships for O(2) and facilitate O(2) diffusion along PO(2) gradients. MATERIALS AND METHODS: Mitochondrial respiration was compared in situ in saponin-skinned fibers isolated from the soleus muscles of Wistar rats, in solution enriched in O(2) by injection or the electrolytic process 1) at an O(2) concentration decreasing from 240 µmol/L to 10 µmol/L (132 mmHg to 5 mmHg), with glutamate–malate or N, N, N′, N′-tetramethyl-p-phenylenediamine dihydrochloride (TMPD)–ascorbate (with antimycin A) as substrates; and 2) at increasing adenosine diphosphate (ADP) concentration with glutamate–malate as substrate. RESULTS: As expected, maximal respiration decreased with O(2) concentration and, when compared to glutamate–malate, the apparent Km O(2) of mitochondria for O(2) was significantly lower with TMPD–ascorbate with both waters. However, when compared to the water enriched in O(2) by injection, the Km O(2) was significantly lower with both electron donors in water enriched in O(2) by electrolysis. This was not associated with any increase in the sensitivity of mitochondria to ADP; no significant difference was observed for the Km ADP between the two waters. CONCLUSION: In this experiment, a higher affinity of the mitochondria for O(2) was observed in water enriched in O(2) by electrolysis than by injection. This observation is consistent with the hypothesis that O(2) diffusion can be facilitated in water enriched in O(2) by the electrolytic process.