Serum and brain aminopeptidase activities in cyclic rats

Research into the functional role of brain peptides is performed, in part, by studying peptidase enzymes which might be involved in the processing or inactivation of the brain peptides. Aminopeptidase activity has been proposed as a candidate for the regulation of the degradation of these peptides. In this paper, acid (Asp-) and basic (Arg-) aminopeptidase activities were studied in several brain regions and in the serum during the estrous cycle of the rat. Asp-aminopeptidase activity did not significantly change at any point. However, a marked rise was found in Arg-aminopeptidase activity in all the brain areas studied and the serum during the proestrus. It is suggested that this activity plays a role in the hormonal changes that take place during the cycle, possibly in regulating the activity of several neuroactive peptides.