Quantitative contribution of systemic vascular autoregulation in acute hypertension in conscious dogs.

Abstract

Experiments were performed in nine conscious dogs to quantitate the contribution of systemic vascular autoregulation to the increases in total peripheral resistance (TPR) and mean arterial pressure (MAP) produced by angiotensin II (ANG II), arginine vasopressin (AVP), and norepinephrine (NE). We hypothesized that if autoregulatory vasoconstriction is significant, then the increase in TPR produced by vasoconstrictor infusion will be greater when MAP is controlled at hypertensive values than when the increase in pressure is prevented by controlling MAP at the animal's normotensive value. Each drug was infused at a dose sufficient to increase MAP by 50%. Then, a constant rate of vasoconstrictor infusion was maintained while MAP was controlled at hypertensive or normotensive levels for 15-min periods using a gravity reservoir connected to the left common carotid artery. During AVP infusion, TPR was significantly greater when MAP was controlled at hypertensive than at normotensive values. This autoregulatory-mediated vasoconstriction accounted for approximately three-fourths of the increase in MAP produced by AVP. No significant autoregulatory component was identified for the increases in TPR and MAP produced by ANG II or NE. We conclude that systemic vascular autoregulation is a powerful physiological property that contributes to the hemodynamic response to pressor doses of AVP.

Sphingosine-1-Phosphate–Dependent Activation of p38 MAPK Maintains Elevated Peripheral Resistance in Heart Failure Through Increased Myogenic Vasoconstriction

“…21 Accordingly, the majority of PE-mediated increases in MAP in conscious dogs 14 (and hamsters 41 ) has been shown to depend on a myogenic mechanism. 13,14,42 As hypothesized, mesenteric arteries from mice with post-MI HF displayed a dramatic increase in myogenic response as compared to controls. This may explain the increased PR observed in mice with HF in vivo, in the absence of any overt alteration in the Ca 2ϩ sensitivity of isolated mesenteric arteries.…”

“…Supporting this premise, the maintenance of peripheral vascular tone largely depends on "myogenic" mechanisms intrinsic to vascular smooth muscle cells (VSMCs). 13 On a local level, myogenic mechanisms serve to adapt vascular tone to changes in transmural pressure. Systemically, myogenic vasoconstriction can amplify vasopressor responses by positive feedback on systemic blood pressure.…”

Sphingosine-1-Phosphate Signaling Regulates Myogenic Responsiveness in Human Resistance Arteries

“…The myogenic response serves several critical roles in the microcirculation, including: preserving constant tissue perfusion at varying systemic pressures (autoregulation) [ 3 , 4 ], maintaining proper capillary hydrostatic pressure [ 27 , 28 ] and, by generating a significant proportion of peripheral resistance, contributing to systemic blood pressure control [ 5 , 6 ]. The complex molecular mechanisms that underpin this response display remarkable heterogeneity across species and vascular bed (reviewed by Lidington et al [ 12 ]): this obstacle has undoubtedly hindered the development of pharmaceuticals that specifically target microvascular tone (e.g., as an anti-hypertensive agent).…”

Cerebral artery myogenic reactivity: The next frontier in developing effective interventions for subarachnoid hemorrhage

“…For example, in the hamster cheek pouch, third-order resistance arteries (28 mm) exhibit $23% greater myogenic index (i.e., the slope of the pressure-diameter relationship) than the first-order arteries (81 mm). 67 This indicates that the smaller resistance arteries are of particular functional importance for blood pressure regulation, 68,69 the protection of downstream capillary integrity 38,39 and minimization of edema formation. 70 The molecular basis for the myogenic response has been extensively reviewed; 52,53,55,56 since this is a substantial topic in its own right, this review will provide a simplified and abbreviated overview.…”