280
This species difference in xenobiotic receptor / ligand signaling may be attributable to differences in the expression level of a receptor , or to differences in receptor / ligand binding affinity , and causes difficulty in determining responses in humans based on rodent data [ 56 ] .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Anatomy 
Text: {0} 
Answer:
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