Renal Salt Handling in Postural Tachycardia Syndrome Following Dietary Dopa Administration

The purpose of this study is to learn how plants can play a role in gain/loss of sodium in the urine and in the regulation of blood pressure. Dopamine is a chemical mostly present in the brain and kidneys which assists in regulation of the body's salts (sodium and potassium). Fava beans contain a lot of the chemical that increases the production of dopamine by the kidneys.

The purpose of these studies is to characterize the diuretic effects of dietary catecholamine sources in healthy individuals. Specific aims are:

1. To determine the effect of dietary dopa sources on plasma and urinary catecholamines.
2. To investigate the capacity of botanical dopaminergic agents (fava beans) to induce natriuresis in a short term study.
3. To provide preliminary data on the effects of dietary dopa on heart rate and blood pressure.

In these studies, we will test the null hypothesis (Ho) that urinary sodium excretion will not differ in healthy volunteers after consumption of a fixed-sodium study diet and the study diet plus fava beans.

Fava beans are a broad bean, with potential clinical relevance in Parkinson's patients since they contain high levels of the dopamine precursor, dihydroxyphenylalanine (dopa).In addition to the central nervous system functions of dopamine that are compromised in Parkinson's disease, renal dopamine has vasodilatory and natriuretic activity. Elevated urinary dopamine, however, does not consistently correlate with increased urinary sodium excretion, and there are conflicting opinions over the conditions under which renal dopamine might regulate sodium balance.The goal of our study was to clarify the natriuretic effect of fava beans, obtained from a source that serves patients with Parkinson's disease. Catechol and sodium data were compared in healthy volunteers using a longitudinal design in which all participants consumed a fixed sodium study diet on day 1 and the fixed sodium diet plus fava beans on day 2. Blood was sampled at 1, 2, 4 and 6 hours after breakfast, and three consecutive 4-hr urine samples were collected.

Postural tachycardia syndrome (POTS) is the most common form of orthostatic intolerance, affecting an estimated 500,000 Americans, principally young women. POTS refers to an excessive increase in heart rate (\>30 beats per minute) on standing in the absence of orthostatic hypotension. Previous findings by the Robertson/Garland research group suggest that mechanisms involved in orthostatic and absolute volume regulation contribute to POTS pathophysiology. A follow-up study might compare the influences of diet in patients with POTS and healthy volunteers.

Eligibility Criteria:
Inclusion Criteria:

* Non-smoking
* Free of medications with the potential to influence BP
* Age between 18-60 years
* Male and female subjects are eligible
* Able and willing to provide informed consent

Exclusion Criteria:

* Significant cardiovascular, pulmonary, hepatic, or hematological disease by history or screening results
* Positive urine b-hcg pregnancy test
* Evidence of cardiac structural disease (by clinical examination or prior echocardiogram)
* Hypertension defined as a BP\>145/95 (off medications) or need for antihypertensive medications
* Evidence of significant conduction system delay (QRS duration \>120 ms) on electrocardiogram
* Inability to give, or withdraw, informed consent
* Other factors which in the investigator's opinion would prevent the subject from completing the protocol Food allergies to favas or other dietary dopa sources selected
* Parkinson's Disease
* Diagnosis of Glucose-6-Phosphate Dehydrogenase (G6P) Deficiency or Individuals from the Mediterranean with family history of G6PD.
* Prolonged QT interval on ECG\> 480 13. Familial history of sudden cardiac death