S. Murphy et al., EFFECT OF HYPOXIA AND REOXYGENATION ON THE ACTIVITY OF TRANSGLUTAMINASE IN BRAIN OF NEWBORN PIGLETS, Neuroscience letters, 172(1-2), 1994, pp. 42-46
The transglutaminase activity in five regions of the brain of newborn
piglets was measured and the effects of hypoxia and posthypoxic period
on this activity evaluated. Enzyme activity was measured in homogenat
es from cortex, hippocampus, striatum, thalamus and midbrain. The cont
rol activities were 7.2, 6.2, 6.0, 5.7 and 4.6 pmol/mg protein/min, re
spectively. The activities at the end of an 18 min period of hypoxia i
nduced by an FiO2, of 9% were not significantly different from control
activities. By 3 h after the hypoxic episode, however, the transgluta
minase activites were significantly above control levels in all five r
egions of the brain. Measurements of the kinetic constants of tranglut
aminase indicated that increases in enzyme activity were associated wi
th an increase in Vmax with no significant change in the apparent affi
nity of the enzyme for the substrate, putrescine. The increased activi
ty of transglutaminase during the posthypoxic period, with no changes
immediately after hypoxia, suggest that the increases could be due to
increased enzyme synthesis rather then activation of existing enzyme.
The rise in transglutaminase activity subsequent to a hypoxic episode
may contribute significantly to the long-term disturbances in cellular
metabolism in the immature brain induced by hypoxic episodes.