Renal vasoconstriction is augmented during exercise in patients with peripheral arterial disease.

Peripheral arterial disease (PAD) patients have augmented blood pressure increases during exercise, heightening their cardiovascular risk. However, it is unknown whether patients have exaggerated renal vasoconstriction during exercise and if oxidative stress contributes to this response. Eleven PAD patients and 10 controls (CON) performed 4-min mild, rhythmic, plantar flexion exercise of increasing intensity (0.

Effect of oxidative stress on sympathetic and renal vascular responses to ischemic exercise.

Reactive oxygen species (ROS), produced acutely during skeletal muscle contraction, are known to stimulate group IV muscle afferents and accentuate the exercise pressor reflex (EPR) in rodents. The effect of ROS on the EPR in humans is unknown. We conducted a series of studies using ischemic fatiguing rhythmic handgrip to acutely increase ROS within skeletal muscle, ascorbic acid infusion to scavenge free radicals, and hyperoxia inhalation to further increase ROS production.

Aspirin augments carotid-cardiac baroreflex sensitivity during muscle mechanoreflex and metaboreflex activation in humans.

Muscle mechanoreflex activation decreases the sensitivity of carotid baroreflex (CBR)-heart rate (HR) control during local metabolite accumulation in humans. However, the contribution of thromboxane A2 (TXA2) toward this response is unknown. Therefore, the effect of inhibiting TXA2 production via low-dose aspirin on CBR-HR sensitivity during muscle mechanoreflex and metaboreflex activation in humans was examined.

Effect of healthy aging on renal vascular responses to local cooling and apnea.

Sympathetically mediated renal vasoconstriction may contribute to the pathogenesis of hypertension in older adults, but empirical data in support of this concept are lacking. In 10 young (26 ± 1 yr) and 11 older (67 ± 2 yr) subjects, we quantified acute hemodynamic responses to three sympathoexcitatory stimuli: local cooling of the forehead, cold pressor test (CPT), and voluntary apnea. We hypothesized that all stimuli would increase mean arterial blood pressure (MAP) and renal vascular resistance index (RVRI) and that aging would augment these effects.

Tactile stimulation of the oropharynx elicits sympathoexcitation in conscious humans.

Tactile stimulation of the oropharynx (TSO) elicits the gag reflex and increases heart rate (HR) and mean arterial pressure (MAP) in anesthetized patients. However, the interaction between upper-airway defense reflexes and the sympathetic nervous system has not been investigated in conscious humans. In Experiment 1, beat-by-beat measurements of HR, MAP, muscle sympathetic nerve activity (MSNA), and renal vascular resistance (RVR) were measured during TSO and tactile stimulation of the hard palate (Sham) in the supine posture.

Cardiac mechanics are impaired during fatiguing exercise and cold pressor test in healthy older adults.

We sought to determine how the aging left ventricle (LV) responds to sympathetic nervous system (SNS) activation. Three separate echocardiographic experiments were conducted in 11 healthy young (26 ± 1 yr) and 11 healthy older (64 ± 1 yr) adults. Tissue Doppler imaging was used to measure systolic myocardial velocity (S(m)), early diastolic myocardial velocity (E(m)), and late diastolic myocardial velocity (A(m)) during isometric fatiguing handgrip (IFHG), a 2-min cold pressor test (CPT), and 5 min of normobaric hypoxia.

Oxidative stress contributes to the augmented exercise pressor reflex in peripheral arterial disease patients.

Exaggerated blood pressure (BP) responses to dynamic exercise predict cardiovascular mortality in patients with peripheral arterial disease (PAD). However, the underlying mechanisms are unclear and no attempt has been made to attenuate this response using antioxidants. Three physiological studies were conducted in patients with PAD and controls.

Aging attenuates the coronary blood flow response to cold air breathing and isometric handgrip in healthy humans.

The purpose of this echocardiography study was to measure peak coronary blood flow velocity (CBV(peak)) and left ventricular function (via tissue Doppler imaging) during separate and combined bouts of cold air inhalation (-14 ± 3°C) and isometric handgrip (30% maximum voluntary contraction). Thirteen young adults and thirteen older adults volunteered to participate in this study and underwent echocardiographic examination in the left lateral position. Cold air inhalation was 5 min in duration, and isometric handgrip (grip protocol) was 2 min in duration; a combined stimulus (cold + grip protocol) and a cold pressor test (hand in 1°C water) were also performed.