Abstract
This investigation related arterial structure to myogenic (pressure-dependent) contractile responses in resistance arteries from spontaneously hypertensive rats (SHRs) and Wistar-Kyoto (WKY) normotensive control rats under pressurized conditions in vitro. Femoral and mesenteric resistance arteries from either strain were cannulated and pressurized in an arteriograph for the determination of pressure-diameter relationships under passive and active conditions in the range 5-200mmHg transmural pressure. Arterial geometrical measurements were made under relaxed conditions at 100mmHg. Media thickness/lumen diameter (M/L) ratios were significantly increased in SHR femoral (5.00±0.44% compared with 3.63±0.34%; PPin vivo pressures under passive and active conditions are similar in SHR and WKY rat arteries. These data demonstrate that increased M/L ratios in resistance arteries from SHRs are not associated with increased maximum pressure-dependent contractile responses. Increased M/L ratios in resistance arteries from SHRs are not accounted for by increased vessel wall stiffness, but the hypertension-associated arterial geometrical abnormalities act to normalize wall stress in the face of increased arterial pressure.

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