Increase of 5?-nucleotidase activity in some brain subcellular fractions after the administration of the convulsant 3-mercaptopropionic acid.

5?-Nucleotidase activity was studied in subcellular fractions isolated from rat brain after the administration of the convulsant 3-mercaptopropionic acid. The results obtained showed that the activity of this membrane enzyme increased in the fractions of the cerebral cortex containing nerve endings and microsomes (Mic(20) and Mic(100)) isolated during the seizure, but not in the post-seizure period. This increase could be observed at pH 7.2 and 9.0 but not at pH 6.5. 5?-Nucleotidase activity in nuclear and myelin fractions did not differ between fractions from control and treated animals. It is suggested that the alteration in enzyme activity found in some brain fractions might be involved in the actions of adenosine during the convulsive seizure.