Vascular Responses to Sympathetic Activation and Altered Shear Rate: The Impact of Hypertension and Sodium Intake

Sodium intake is a major contributor to the development of hypertension in the developed
world. Interestingly, it has been recently revealed that, in addition to the cardiovascular
dysfunction associated with high sodium intake-induced hypertension, individuals who have
unaltered blood pressure after chronic high sodium intake, termed salt resistant, report
similar reductions in cardiovascular function when compared to salt sensitive individuals.
While the extent to which this high sodium intake negatively alters cardiovascular structure
as well as function is currently being explored, little is known about how high sodium intake
impacts vascular function and blood flow regulation during exercise. Therefore, this study
will determine if alterations in sodium intake alter peripheral vascular function and
exercise tolerance in young individuals. The investigators hypothesize that increases in
sodium intake will reduce exercise-induced arterial dilation in response to shear and result
in exercise intolerance, via impaired functional sympatholysis, at moderate-to-high exercise
workloads. Furthermore, the investigators hypothesize that these changes in blood flow
regulation and exercise tolerance in young individuals will be reversed following antioxidant
supplementation, implicating the role of oxidative stress in this dysfunction.

Inclusion Criteria:

- normotensive blood pressure (Systolic <120 AND Diastolic <80

- free of cardiovascular disease and any evidence of thyroid, renal, metabolic,
pulmonary or neurological disease

- non-obese (BMI <30 and/or Body fat < 25% for men, and < 30% for women)

- no tobacco use

- no medications that could affect vascular function or oxidative stress

- not sedentary

Exclusion Criteria:

- individual with cardiovascular, pulmonary, or metabolic disease or taking medications
that may alter cardiovascular, pulmonary, or metabolic function

- subjects will be asked to maintain a dietary record for one week subsequent to the
pre-screening and if this reveals a diet that differs substantially from the "typical"
average diet, the subject will not be eligible

- subjects will be excluded from the study if dietary records reveal significant caloric
restriction and/or vitamin/mineral deficiencies

- pregnant women, prisoners, and children will not be eligible for this study