Levels of brain angiotensin in the spontaneously hypertensive rat and treatment with ramiprilat.

Previous studies have indicated that brain angiotensin II (ANG II) in the spontaneously hypertensive rat (SHR) may play an important role in the maintenance of hypertension. Preventing the synthesis of ANG II leads to a reduction in blood pressure and, therefore, brain ANG II levels in the SHR should be higher or have increased turnover than in the Wistar-Kyoto (WKY) rat. To investigate this issue we have dissected discrete areas of the brain from SHR and WKY and extracted, purified and quantified brain ANG II. Significantly higher levels were found in the hypothalamus, striatum, cortex and cerebellum in SHR compared to WKY. The new converting enzyme inhibitor, ramiprilat, injected centrally lowered blood pressure by synthesis inhibition but measurements of brain ANG II after ramiprilat did not indicate increased turnover. Further analysis of the peptide fragments needs to be done before turnover rates can be fully understood.