Abstract
The activity of the angiotensin-converting enzyme (ACE) was measured in serum and brain microvessels of adult stroke-prone spontaneously hypertensive rats (SHR-SP), stroke-resistant spontaneously hypertensive rats (SHR-SR) and Wistar Kyoto Rats (WKY). In brain microvessels, SHR (SHR-SR+SHR-SP) were found to have reduced ACE activity as compared to WKY. Furthermore the activity of this enzyme was significantly lower in SHR-SP than that in SHR-SR. ACE activity was inversely related to the systolic blood pressure. γ-GTP activity and prostaglandin I2 release, either basal or stimulated with arachidonic acid, from isolated brain microvessels were similar in the three groups. Serum ACE activity was greatly decreased in SHR. In contrast to brain microvessels, SHR-SP showed higher activity than SHR-SR and the difference was significant. There was no correlation in ACE activity between serum and brain microvessels. The marked reduction of ACE activity in brain microvessels of SHR-SP may be relevant to the endothelial damage or the pathogenesis of vascular lesions in that animal model.
