Hypoxia and ischemia modifies histamine metabolism and transport in brain synaptosomes.

Histamine level (HA), the activities of the HA synthetizing enzyme--histidine decarboxylase (HD) and HA metabolizing enzyme--histamine methyltransferase (HMT) and the uptake and release of histidine and histamine were analyzed in synaptosomal preparations obtained from rats with brain hypoxia and ischemia. Hypoxia produced only non-significant changes in all the parameters studied, whereas ischemia induced increase of both enzyme activities and histidine release, with simultaneous decreased of histidine uptake and HA level. The effect of ischemia appeared to be reversible; the changes retreated within 1 h of resuscitation together with the vital functions of rats.