The effect of morphine, naloxone, D- and L-aspartic acid on the brain and lung ACE in mice

Abstract

The brain and lung angiotensin converting enzyme (ACE) activities of the mice injected with 10 mg/kg morphine and/or naloxone, 200 mg/kg D- and/or L-aspartic acid were spectrophotometrically determined. Morphine, naloxone, D- and L-aspartic acid alone inhibited both brain and lung ACE activities whereas the combinations of morphine with naloxone, D-aspartic acid with L-aspartic acid and morphine with naloxone + L-aspartic acid showed no inhibitory effect on the brain ACE. While naloxone or L-aspartic acid partly antagonized the suppression of morphine on the lung ACE their combination completely prevented morphine from inhibiting the lung ACE. In the in vivo experiments performed on the brain and lung homogenates of the untreated mice the determination of the ACE activity in the incubating media containing 3.10(-3) M morphine or naloxone, 10(-2) M D- or L-aspartic acid showed a significant decrease in the activity. But no in vitro antagonistic effect was found by using the combinations of the drugs used in the study. The antagonism seen in the in vivo experiments was considered as an indirect one. And the relationship between the inhibitory effect of morphine, naloxone and D-aspartic acid, their suppressive effect on drinking and their beneficial effects in various forms of shock was discussed.