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: Mitochondrial calcium - loading capacity and the activity of NADH - dehydrogenase were also suppressed in cardiac mitochondria from doxorubicin - treated rats .
### Output Text:
Mitochondrial <span class="chemical">calcium</span> - loading capacity and the activity of NADH - dehydrogenase were also suppressed in cardiac mitochondria from <span class="chemical">doxorubicin</span> - treated rats . 