Extracellular measurements of ATP: From blood to brain.

摘要

Adenosine triphosphate (ATP) is one of the most well known intracellular molecues due to its primary role of driving chemical reactions forward. However, the role of ATP in the last few decades has been expanded to an extracellular signaling molecule. The two functions of ATP that were characterized in this thesis are ATP release from red blood cells (RBCs) and ATP's role as a neurotransmitter/signaling molecule. Previous work has shown that as a RBC traverses through microvessels, it releases high nanomolar to low micromolar amounts of ATP due to mechanical deformation. The ATP released stimulates nitric oxide (NO) production from endothelial cells that line the vessel walls, resulting in vasodilation. Recent publications revealed that RBCs from diabetic patients release less ATP than normal RBCs. This may be due to a weakened oxidant defense system which makes the red cell membrane less deformable. Therefore, a decrease in ATP release could result in decreased NO production, vasodilation, and lead to many of the complications associated with diabetes, such as hypertension and stroke. Two drugs commonly prescribed that are known to increase the release of ATP from RBCs are pentoxifylline and iloprost, although their mechanism of action is unknown. Therefore, the primary objective of this thesis was two fold (1) determine the mechanism of action of these drugs with relation to ATP and (2) evaluate their effectiveness under conditions of oxidative stress such as diabetes. Results suggest pentoxifylline and iloprost may help increase the release of ATP from RBCs even under conditions of oxidative stress and may play a role in improving complications from diabetes.;Thirty years ago Burnstock proposed that ATP was a neurotransmitter, however the acceptance of ATP as a neurotransmitter has been slow. Within the brain, ATP plays a crucial role because its degradation product is the neurotransmitter adenosine. Extracellular ATP levels have been a matter of debate in the literature. Therefore, the first objective was to develop a fast and selective method for quantitating extracellular ATP levels. The second objective was to evaluate ATP levels under a traumatic insult (stroke, ischemia) and monitor ATP levels in real time. Overall, the data presented in this thesis represent that ATP is indeed a critical molecule.