Effects of Ca2+ and lipoxygenase inhibitors on hexokinase degradation in rabbit reticulocytes

In rabbit reticulocytes more than half of the total hexokinase activity is mitochondrial bound and shows a fast decay during reticulocyte maturation. During in vitro incubation of rabbit reticulocytes, Ca2+ increases the decay of hexokinase while salicylhydroxamate (SHAM), an inhibitor of lipoxygenase, reduces the decay. Swelling of mitochondria, by incubation of the cells in hypotonic solutions, greatly enhances hexokinase decay, but both the Ca2+ and SHAM are still appreciable suggesting that Ca2+ and the swelling act by additive mechanisms, both able to influence hexokinase decay. This was confirmed by incubation of rabbit brain mitochondria in hypotonic solutions which does not promote any hexokinase decay, while the presence of Ca2+ does. Analyses of hexokinase isozymic pattern after incubation of reticulocytes in hypotonic solution both with and without Ca2+ and SHAM showed that the decay of hexokinase mainly involves the mitochrondrial bound isozymic forms.