Extracellular ATP (eATP) plays a significant role in various physiological and pathological processes. While traditionally thought to be confined within cells, eATP is released into the extracellular environment and interacts with specific receptors on the surface of many cell types. These interactions can influence platelet aggregation, vascular tone, neurotransmission, cardiac function, and muscle contraction. eATP is released from various cell types, including platelets and neurons, and is metabolized by ectonucleotidases. Receptors that recognize ATP are classified into P1 and P2 receptors. P2 receptors, which are more relevant to this review, are further subdivided into different classes based on their response to ATP and other nucleotides. These receptors are involved in various physiological functions, including platelet aggregation, mast cell secretion, and vascular responses. The P2 receptors can be further classified into subclasses such as T, X, Y, and Z, each with distinct characteristics and functions. ATP induces platelet aggregation and affects the release of histamine from mast cells. It also influences membrane permeability and can lead to the release of intracellular metabolites. In the cardiovascular system, eATP can induce vasodilation through the release of endothelium-derived relaxing factor (EDRF) and prostacyclin. However, in some cases, eATP can cause vasoconstriction, particularly in the presence of endothelial dysfunction. In non-vascular smooth muscle, ATP can modulate smooth muscle tone and influence gastrointestinal motility. ATP also plays a role in neuromodulation, acting as a neurotransmitter or modulating the release of other neurotransmitters. In the central nervous system, ATP can have inhibitory effects on neuronal activity. In the context of shock, ATP can have both beneficial and harmful effects. While high concentrations of ATP can be toxic, moderate levels can improve tissue function and blood flow. ATP is released from various sources, including purinergic nerve terminals, cells in or adjacent to the circulating blood, and other cells. The release of ATP is influenced by various stimuli, and its concentration in the extracellular space is regulated by ectonucleotidases. The metabolism of eATP is primarily carried out by ectonucleotidases, which break down ATP into ADP, AMP, and adenosine. These enzymes are widely distributed in various tissues and play a crucial role in regulating the concentrations of extracellular purines. The study of eATP has revealed its diverse roles in physiological and pathological processes, highlighting the importance of understanding its sources, effects, and metabolism.Extracellular ATP (eATP) plays a significant role in various physiological and pathological processes. While traditionally thought to be confined within cells, eATP is released into the extracellular environment and interacts with specific receptors on the surface of many cell types. These interactions can influence platelet aggregation, vascular tone, neurotransmission, cardiac function, and muscle contraction. eATP is released from various cell types, including platelets and neurons, and is metabolized by ectonucleotidases. Receptors that recognize ATP are classified into P1 and P2 receptors. P2 receptors, which are more relevant to this review, are further subdivided into different classes based on their response to ATP and other nucleotides. These receptors are involved in various physiological functions, including platelet aggregation, mast cell secretion, and vascular responses. The P2 receptors can be further classified into subclasses such as T, X, Y, and Z, each with distinct characteristics and functions. ATP induces platelet aggregation and affects the release of histamine from mast cells. It also influences membrane permeability and can lead to the release of intracellular metabolites. In the cardiovascular system, eATP can induce vasodilation through the release of endothelium-derived relaxing factor (EDRF) and prostacyclin. However, in some cases, eATP can cause vasoconstriction, particularly in the presence of endothelial dysfunction. In non-vascular smooth muscle, ATP can modulate smooth muscle tone and influence gastrointestinal motility. ATP also plays a role in neuromodulation, acting as a neurotransmitter or modulating the release of other neurotransmitters. In the central nervous system, ATP can have inhibitory effects on neuronal activity. In the context of shock, ATP can have both beneficial and harmful effects. While high concentrations of ATP can be toxic, moderate levels can improve tissue function and blood flow. ATP is released from various sources, including purinergic nerve terminals, cells in or adjacent to the circulating blood, and other cells. The release of ATP is influenced by various stimuli, and its concentration in the extracellular space is regulated by ectonucleotidases. The metabolism of eATP is primarily carried out by ectonucleotidases, which break down ATP into ADP, AMP, and adenosine. These enzymes are widely distributed in various tissues and play a crucial role in regulating the concentrations of extracellular purines. The study of eATP has revealed its diverse roles in physiological and pathological processes, highlighting the importance of understanding its sources, effects, and metabolism.