Food Restriction Augmented Alpha1-Adrenergic Mediated Contraction in Mesenteric Arteries

Food restriction (FR) enhances sensitivity to cardiopulmonary reflexes and α1-adrenoreceptors in females in the presence of hypotension. However, the effect of FR on cardiopulmonary and vascular function in males is not well-understood. This study examines the effects of FR on cardiopulmonary, isolated arterial function, and potential underlying mechanisms. Male Sprague-Dawley (SD) rats were randomly divided into 3 groups and monitored for 5 weeks: (1) control (n = 30), (2) 20% food reduction (FR20, n = 30), and (3) 40% food reduction (FR40, n = 30). Non-invasive blood pressure was measured twice a week. Pulmonary arterial pressure (PAP) was measured using isolated/perfused lungs. The isolated vascular reactivity was assessed using double-wire myographs. FR rats exhibited a lower mean arterial pressure and heart rate; however, only the FR40 group exhibited statistically significant differences. We observed that FR enhanced sensitivity (EC₅₀) to vasoconstriction induced by the α1-adrenoreceptor phenylephrine (PhE) but not to serotonin, U46619, or high K⁺ in the mesenteric arteries. PhE-mediated vasoconstriction in the mesenteric arteries was eliminated in the presence of the eNOS inhibitor (L-NAME). In addition, incubation with NOX2/4 inhibitors (apocynin, GKT137831, and VAS2870) and the reactive oxygen species (ROS) scavenger inhibitor (Tiron) eliminated the differences in PhE-mediated vasoconstriction, but the cyclooxygenase inhibitor (indomethacin) in the mesenteric arteries did not. Augmentation of α1-adrenergic-mediated contraction via the inhibition of the eNOS-NO pathway increased the activation of ROS through NOX2/4 in response to FR. Reduced eNOS-NO signaling may be a pathophysiological counterbalance to prevent hypovolemic shock in response to FR.