Passive structural measurements of LMAs from Wistar rats, SHRs treated with hydralazine, captopril or vehicle. A, Changes in passive inner diameter in response to increased intravascular pressure. There was a significant pressure effect [F(1, 213)=500.10, P<0.01], but no significance in pressure by group interaction or group effect [F(3, 213)=0.39, F(3, 27)=2.87; P>0.05]. *P<0.05 vs. Wistar and SHR-Hydral rats by pairwise group comparisons. B, Changes in passive outer diameter in response to increased intravascular pressure. There was a significant pressure effect [F(1, 213)=289.87, P<0.01], but no significance in pressure by group interaction or group effect [F(3, 213)=0.96, F(3, 27)=2.82; P>0.05]. *P<0.05 vs. SHR-Hydral rats by pairwise group comparisons. C, Changes in wall thickness in response to increased intravascular pressure. There was a significant pressure effect [F(1, 213)=115.50, P<0.01], but no significance in group by pressure interaction or group effect [F(3, 213)=1.68, F(3, 27)=0.90, P>0.05]. D, percent distensibility in response to increased intravascular pressure. There was a significant pressure effect [F(1, 213)=534.31, P<0.01], but no significance in pressure by group interaction or group effect [F(3, 213)=0.55, F(3, 27)=0.03; P>0.05]. Wistar: n=8; SHR-Hydral: n=7; SHR-Capto: n=8; SHR-Veh: n=8. Data were analyzed by mixed model repeated measures ANOVA.