Inclusion Criteria:

• * healthy controls age 18-55 yr.
• * Body mass index \>21 kg · m-2

Exclusion Criteria:

• * Pregnant or breastfeeding women
• * Subjects unwilling or unable to comply with approved contraception measures
• * Subjects unable to give voluntary informed consent
• * Subjects on anticoagulant drugs, anemic or with known bleeding diatheses
• * Subjects with a history of severe, uncontrolled hypertension, heart disease, cerebrovascular incidents
• * Current tobacco use
• * Subjects with any known allergies to any of the study medications being used
• Physical Exam Exclusion Criteria
• * Uncontrolled severe hypertension (i.e., blood pressure greater than 160/100)
• * Clinically significant cardiac abnormalities (e.g. heart failure, arrhythmia)
• * Pneumonia treatment or hospitalization within 2 weeks prior to enrollment (study visit)
• * Hepatic failure / jaundice
• * Renal failure
• * Cerebrovascular accident occurrence or hospitalization within 4 weeks prior to enrollment
• * Fever greater than 38.0 degrees C
• Screening Laboratory Tests Exclusion Criteria
• * Hematocrit lower than 32 %
• * White blood cell (WBC) count lower than 3 thou/ul or greater than 14 thou/ul
• * Liver function tests: serum glutamic oxaloacetic transaminase (SGOT) and serum glutamic-pyruvic transaminase (SGPT) greater than twice upper limit of normal range
• * Alkaline phosphatase greater than 150U/L
• * Total bilirubin (TBil) greater than 2 mg/dl
• * Estimated glomerular filtration rate (eGFR) less than 60 mL/min/1.73 m2
• * Positive human immunodeficiency virus (HIV), Hepatitis B or Hepatitis C
• * Any abnormal cardiac response during multi-stage exercise test (if over 40 years of age)