Hydrogen peroxide-dependent arteriolar dilation in contracting muscle of rats fed normal and high salt diets.

Objective: High dietary salt intake decreases the arteriolar dilation associated with skeletal muscle contraction. Because hydrogen peroxide (H2O2) can be released from contracting muscle fibers, this study was designed to assess the possible contribution of H2O2 to skeletal muscle functional hyperemia and its sensitivity to dietary salt.

Methods: The authors investigated the effect of catalase treatment on arteriolar dilation and hyperemia in contracting spinotrapezius muscle of rats fed a normal salt (0.

Functional hyperemia is reduced in skeletal muscle of aged rats.

Objective: To test the hypothesis that active hyperemia is reduced in skeletal muscle of old rats due to a decreased bioavailability of prostanoids, which in turn is due to increased oxidative stress.

Methods: The microvasculature of the spinotrapezius muscle of 3-, 12-, and 24-month male Sprague-Dawley rats was examined using in vivo videomicroscopy. Arteriolar diameter and centerline red cell velocity were measured in resting and contracting muscle.

ATP stimulates the release of prostacyclin from perfused veins isolated from the hamster hindlimb.

ATP-stimulated prostacyclin release from veins was investigated using epigastric veins isolated from hamsters. Veins were perfused with MOPS-buffered physiological salt solution (PSS). ATP was administered into the perfusate, and the bath solution (MOPS-PSS) was collected and assayed for the presence of the stable prostacyclin metabolite 6-keto-PGF1alpha.

Venular-arteriolar communication in the regulation of blood flow.

Muscle blood flow is regulated to meet the metabolic needs of the tissue. With the vasculature arranged as a successive branching of arterioles and the larger, >50 microm, arterioles providing the major site of resistance, an increasing metabolic demand requires the vasodilation of the small arterioles first then the vasodilation of the more proximal, larger arterioles. The mechanism(s) for the coordination of this ascending vasodilation are not clear and may involve a conducted vasodilation and/or a flow-dependent response.

Calcium-dependent synthesis of prostacyclin in ATP-stimulated venous endothelial cells.

Prostacyclin is a powerful vasodilator that is released from vascular endothelial cells. Previous studies in our laboratory have indicated that arachidonic acid metabolites from venous endothelium play an important role in the dilation of adjacent arterioles during muscle stimulation. Furthermore, recent studies have suggested that ATP released from red blood cells during hypoxia stimulates dilation of arterioles.