Abstract

Introduction

Materials & Methods

Results

Discussion & Conclusion

References

Discussion
Board

Objective: To determine the magnitude of the early component of regression of structurally-based vascular resistance properties in adult spontaneously hypertensive rats (SHR) after only 2 weeks of renin-angiotensin system (RAS) inhibition. Design and Methods: SHR treated for 2 wks with equidepressor losartan or enalapril (L=30, E=30 mg/kg per day) were anesthetized and the right hindlimb vasculature isolated and perfused. Maximum dilation was induced, a flow-pressure relationship and an [alpha-1 adrenoceptor agonist]-response curve were generated. Maximum vasoconstriction, shown as a response 'yield', (correlates with average bulk of vascular smooth muscle) was obtained using a cocktail: vasopressin (21 IU/ml), angiotensin II (200ng/ml) and methoxamine (64 ug/ml). Hearts were excised and the separate ventricles weighed. Results: Blood pressure profiles were similar with E and L treatments (29%, 25% reduction)after 2 weeks. Both treatment groups produced similar decrease (18.5%, 18.6%) in structurally-based vascular resistance properties (i.e. 'yield' response) as compared to untreated SHR. Both treatments also induced significantregression of left ventricular mass (L: 12.6%, E: 18.4%) compared with control. Conclusion: After only 2 weeks of RAS unhibition there is marked regression of structurally-based vascular resistance properties in SHR. Previous studies (Harrap et al, 1990) have shown that > 4 weeks of ACE inhibitor treatment are required to produce persistent changes after cessation of treatment. This indicates that the 'type' of regression observed with short term treatment is likely reversible.

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Presentation Number SAhale0778
Keywords: hypertension, structural change, AT1 antagonism, ACE inhibition, shr