LOCALIZATION OF ANGIOTENSIN-CONVERTING ENZYME BY IN-VITRO AUTORADIOGRAPHY IN THE RABBIT BRAIN

The distribution of angiotensin converting enzyme was examined in the rabbit brain by in vitro autoradiography with the specific radiolabell ed inhibitor I-125-351A. In the rabbit, the highest concentrations of radioligand binding were found in the choroid plexus, blood vessels, s ubfornical organ, vascular organ of the lamina terminalis, area postre ma and inferior olive. High levels of binding were found throughout th e basal ganglia, consistent with the results in all other species stud ied. In the midbrain the central gray and the superior colliculus disp layed high levels of binding. In the medulla oblongata high levels of binding were associated with the nucleus of the solitary tract and dor sal motor nucleus of vagus, consistent with the pattern in other speci es. There was moderate labelling throughout both the cerebral and cere bellar cortices, which contrasts to the rat but is consistent with the situation in primates. Angiotensin converting enzyme (ACE) is more wi dely distributed in rabbit brain that in rat, human and Macaca fascicu laris, and the results suggest ACE has a very general role in the meta bolism of neuropeptides. Inhibitors of converting enzyme are very wide ly used in the treatment of hypertension and heart disease, and the ra bbit should provide a useful model for examining the effects of these drugs in the brain.