Remodeling of arterial wall: Response to changes in both blood flow and blood pressure

Many studies have been performed on arterial responses to chronic changes in blood flow (BF) and blood pressure (BP). However, little is known about the effects of simultaneous changes in BF and BP. The present study was carried out to know biomechanical responses of arterial wall to the combination of increased BP, i.e. hypertension (HT), with lower or higher BF than normal, and the results were compared with those observed under normal BP, i.e. normotension (NT), combined with these BF conditions. Eight weeks old rats were subjected to BF and/or BP changes for 8 weeks until 16 weeks of age. Systemic HT was induced by the constriction of one of the renal arteries (Goldblatt HT), while BF in the CCA was reduced and increased by the constriction of the ipsilateral CCA and the ligation of the contralateral CCA, respectively. The internal diameter of the target CCA was significantly larger in higher BF groups than in lower BF ones irrespective of HT. Wall shear stress (WSS) was normalized by such compensatory changes in the diameter. Wall thickness was significantly larger in HT rats than in NT ones regardless of BF, and the wall hypertrophy contributed to restore wall hoop stress to normal level. Basal vascular tone, arterial stiffness, and wall elastic modulus were significantly larger in HT than in NT independently of BF changes. However, only in HT/lower BF group, WSS and vascular smooth muscle-activated vascular contraction were smaller than in the other groups, possibly because of wall hypertrophy induced by HT.