In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: Immunoblotting , immunohistochemistry , and quantitative ( q ) RT - PCR consistently detected a significant decrease in aquaporin - 2 ( AQP2 ) protein expression in both the renal cortex and medulla of lithium - treated + / + mice .
### Output Text:
Immunoblotting , immunohistochemistry , and quantitative ( q ) RT - PCR consistently detected a significant decrease in aquaporin - 2 ( AQP2 ) protein expression in both the renal cortex and medulla of <span class="chemical">lithium</span> - treated + / + mice . 