PERINDOPRIL CHANGES THE MESENTERIC PRESSURE PROFILE OF CONSCIOUS HYPERTENSIVE AND NORMOTENSIVE RATS

Information about how antihypertensive therapy affects the arterial blood pressure profile in conscious animals is at present not available. Here we report measurements of part of the pressure profile in conscious spontaneously hypertensive rats (SHR, n=7) and Wistar-Kyoto (WKY, n=7) rats before and after treatment with the angiotensin-converting enzyme inhibitor perindopril. The previously developed technique that we used, provided simultaneous measurements of the undisturbed arterial blood pressure at the base of mesenteric arcades (P-arc; diameter, approximately 100 mu m) and systemic mean blood pressure (MBP). The ratio P-arc/MBP was 631+/-2% (mean+/-SEM) in SHR and 64+/-3% in WKY rats. When a bolus of perindopril (0.8 mg/kg) was injected into the aorta, P-arc/MBP fell within 2 minutes to 51+/-2% (P<.05) for SHR and 56+/-2% (P<.05) for WKY rats, and these levels were maintained for the next hour. In contrast, MBP did not change for approximately 5 minutes in either strain, whereas after 1 hour MBP still had not changed significantly in WKY rats, but MBP had fallen by 16+/-2% (P<.05) in SHR. The experiments suggest that in the mesentery (1) the elevated resistance in the arterial system in SHR is present in both macroarteries tie, vessels proximal to the base of the arcades) and in the more distal microarteries and veins, (2) for at least 1 hour perindopril caused greater dilation of the microarteries than the macroarteries, and (3) these profound changes in the mesenteric blood pressure profile appear to occur independently of the fall in MBP, indicating that they are not directly associated with the blood pressure drop.