Alterations of arginase activity in scrapie-infected mice and in amyotrophic lateral sclerosis.

We followed the dynamics of arginase activity, the ultrastructural changes, and accumulation of the scrapie agent in the CNS of scrapie-infected mice. The arginase activity has been shown to increase 5-fold within the first 3-4 months of the incubation period followed by subsequent fall at its end. The peak of increased arginase activity coincided with appearance of multilayer membranes, whereas the decrease of this activity was associated with the greatest development of status spongiosus, synaptic degeneration, accumulation of five-layer membranes as well as with maximal accumulation of the scrapie agent in the CNS. Examination of 100 patients with different forms of amyotrophic lateral sclerosis (ALS) revealed a 2-8-fold increase of arginase levels in the cerebrospinal fluid (CSF) as compared with the background levels in the comparative groups of control patients. Similar enzyme alterations in scrapie--and in ALS--are discussed in terms of possible resemblance of their pathogenesis.