The purpose of this study is to extend previous observations in animal models regarding the
effects of adenosine in the release of cytokines to human subjects. We intend to accomplish
this in two study protocols. In the first we will infuse intravenously adenosine and measure
the plasma levels of inflammatory cytokines. In the second one, we will use a microdialysis
technique to infuse intradermally small amounts of adenosine and will measure skin blood
flow and will take a biopsy to measure levels of mRNA for cytokines.
In Protocol 1 we will infuse adenosine at a dose of 80 mcg/kg/min for 30 minutes while
measuring plasma levels of adenosine at different time points, ranging from 30 minutes to 6
hours. Because activation of A2B receptors also mediates the release of inflammatory
cytokines, including IL-6, samples will be taken to measure these and other
In a second protocol, we will administer adenosine intradermically via a microdialysis probe
for 30 minutes while we measure the local effect on skin blood flow using laser Doppler
techniques. One hour after the end of the infusion we will obtain a skin biopsy from the
perfused area for measurement of mRNA for VEGF, IL-8, IL-6 and other cytokines. In addition,
we foresee the possibility of further testing looking for and genetic association between
angiogenesis and adenosine.
These are proof-of-concept pilot studies. We will study up to 12 subjects in each protocol
but an interim analysis will be performed after 6 subjects are studied. This will help us
determine if a trend is observed, to perform power calculations, and determine if more
extensive studies are warranted.
- Age 18-60 yr.
- All potential volunteers will have routine blood test to screen for hepatic, renal,
and hematological abnormalities.
- Body mass index < 27 Kg/m2 .
- Female volunteers of childbearing potential will undergo HCG pregnancy test at
screening and again on the study day.
- Pregnancy 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 history of asthma
- Recent (past three days) use of phosphodiesterase type 5 (PDE5) inhibitors
(sildenafil, tadalafil or vardenafil)
- History of intolerance to adenosine or nitroprusside
- History of methemoglobinemia
- Use of theophylline products
- Subjects with hematological abnormalities