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Endogenous nucleotides have widespread actions in the cardiovascular system , but it is only recently that the P2X and P2Y receptor subtypes , at which they act , have been identified and subtype - selective agonists and antagonists developed .
 Chemical: nucleotides
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: nucleotides