Extracellular Nucleotide and Nucleoside Signaling: First Principles Introduction: ATP and its Metabolites as Potent Extracellular Agents Cellular Mechanisms and Physiology of Nucleotide and Nucleoside Release from Cells: Current Knowledge, Novel Assays to Detect Purinergic Agonists, and Future Directions Molecular and Biological Properties of P2Y Receptors Extracellular ATP-gated P2X Purinergic Receptor Channels Molecular and Cell Biology of Adenosine Receptors Relating the Structure of ATP-gated Ion Channel-receptors to their Function Epithelial Purinergic Receptors and Signaling in Health and Disease Nucleotide Release and Purinergic Signaling in the Vasculature Driven by the Red Blood Cell A Purine Signal for Functional Hyperemia in Skeletal and Cardiac Muscle Purinergic Receptors in the Nervous System Purinergic (P2) Receptors in the Kidney Purinergic Receptors and Hepatobiliary Function ATP in the Treatment of Advanced Cancer Purinergic Receptors in the Glomerulus and Vasculature of the Kidney