Effect of captopril (a converting enzyme inhibitor) on blood-brain barrier permeability and cerebral blood flow in normotensive rats.

Intracarotid (10 mg/kg), intracerebroventricular (100, 200 micrograms) or topical application (0.8 M) of captopril (a converting enzyme inhibitor) increased the permeability of the blood-brain barrier to Evans blue albumin (EBA) and [131I]sodium in anesthetized normotensive rats. The permeability of the blood-brain barrier to albumen in 6 and to [131I]sodium in 10 out of 14 regions of the brain was increased in the perfused hemisphere after infusion of captopril into the right carotid artery. These regions of the brain were associated with a 54-107% increase in regional cerebral blood flow (CBF). Pretreatment with indomethacin and aprotinin prevented both the increased regional permeability of the blood-brain barrier along with regional cerebral blood flow. Pretreatment with vinblastine prevented only the regional increase in permeability of the blood-brain barrier. The regional cerebral blood flow continued to remain high. The probable mechanism(s) underlying the increased cerebral blood flow and permeability of the blood-brain barrier after infusion of captopril is discussed.