Formation of des-Asp-angiotensin I in the Hypothalamic Extract of Normo- and Hypertensive Rats

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Abstract
Exogenous angiotensin I (ANG I) was degraded to mainly des-Asp-ANG I instead of ANG II in the hypothalamic homogenate of the Sprague Dawley (SD), Wistar Kyoto (WKY), left renal artery stenosed hypertensive SD (LRAS), deoxycorticosterone acetate/salt-induced hypertensive SD (DOCA-salt) and spontaneously hypertensive rats (SHR). In the same homogenate, ANG II was degraded to ANG III and ANG III remained unchanged during the first 10 min of incubation. However, all the homogenates were able to catalyse hippuryl-L-histidyl-L-leucine to hippuric acid and the catalysis was completely inhibited by 3 μM captorpil. The data show that the angiotensin converting enzyme present in the hypothalamus when extracted by the normal laboratory procedures is not able to hydrolyse ANG I to ANG II. In addition, the aminopeptidase that degraded ANG I to des-Asp-ANG I was not inhibited by amastatin, bestatin and EDTA, indicating that it is not aminopeptidase A or B. The formation of hippuric acid was significantly higher in the homogenate of the LRAS whilst the SHR and DOCA-salt showed significant higher rate of des-Asp-ANG I formation than in the normotensive control rats.