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: The decreased capacity to concentrate urine is likely due to lithium acutely disrupting the cAMP pathway and chronically reducing urea transporter ( UT - A1 ) and water channel ( AQP2 ) expression in the inner medulla .
### Output Text:
The decreased capacity to concentrate urine is likely due to <span class="chemical">lithium</span> acutely disrupting the <span class="chemical">cAMP</span> pathway and chronically reducing <span class="chemical">urea</span> transporter ( UT - A1 ) and water channel ( AQP2 ) expression in the inner medulla . 