The investigators are interested in the role of the autonomic nervous system in the regulation of endothelial function among obese hypertensive subjects. In particular, the investigators will study how endothelial function (response to intra-arterial acetylcholine) changes during autonomic withdrawal.

For lean healthy volunteers:

• 20 subjects (10 males and 10 females) aged 18-60 yr.
• All potential volunteers will have routine blood test to screen for hepatic, renal, and hematological abnormalities.
• Body mass index < 25Kg/m2 .
• Female volunteers of childbearing potential will undergo HCG pregnancy test at screening and again on the study day.

For Obese subjects with high blood pressure.

• 20 subjects (10 males and 10 females) aged 18-60 yr.

• All potential volunteers will have routine blood test to screen for hepatic, renal, and hematological abnormalities.

• Body mass index > 30 and less than 40 Kg/m2

  *High blood pressure (systolic=130 and diastolic = 85 mmHg)

• Female volunteers of childbearing potential will undergo serum HCG pregnancy test at screening and urine HCG pregnancy test again on the study day.

Exclusion criteria:

• Pregnant females
• Subjects unable to give voluntary informed consent
• Subjects on anticoagulant drugs or anemic
• Subjects with a recent medical illness
• Subjects with a history of coronary heart disease
• Subjects with known kidney or liver disease
• Subjects with recent weight loss or consuming low carbohydrate diet