DEVELOPMENTAL-CHANGES OF ENZYMES INVOLVED IN PEPTIDE DEGRADATION IN ISOLATED RAT-BRAIN MICROVESSELS

The specific activities of aminopeptidase A (APA), aminopeptidase M (A PM), and dipeptidyl-aminopeptidase IV (DP IV) were determined in isola ted brain microvessels and in brain homogenate of rats with different ages (between 1 and 8 weeks old). In addition, the blood-brain barrier (BBB)-specific enzymes gamma-glutamyltranspeptidase (gamma-GT) and al kaline phosphatase (ALP) were measured. As similarly described by othe rs, gamma-GT activity increased during this time period by fourfold, w hereas ALP increased between weeks 1 and 2 and declined thereafter. DP IV activity increased fivefold during the first 8 weeks after birth a nd APM activity increased by twofold. A decrease of APA activity was f ound between weeks 1 and 2 after birth followed by an increase thereaf ter. The development of aminopeptidase activities responsible for the processing of specific neuropeptides acting on brain microvessels may be important in the development of regulation processes for cerebral b lood flow and BBB permeability in the maturing animal.