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: A significant rise in cTnT was found in DOX rats after cumulative doses of 7 . 5 and 12 mg / kg in comparison with baseline ( p < 0 . 05 ) .
### Output Text:
A significant rise in cTnT was found in <span class="chemical">DOX</span> rats after cumulative doses of 7 . 5 and 12 mg / kg in comparison with baseline ( p < 0 . 05 ) . 