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: In epinephrine - treated rats , left atrial and left ventricular papillary muscle contractile responses to isoproterenol were reduced , but responses to calcium were normal or enhanced compared to controls .
### Output Text:
In <span class="chemical">epinephrine</span> - treated rats , left atrial and left ventricular papillary muscle contractile responses to <span class="chemical">isoproterenol</span> were reduced , but responses to <span class="chemical">calcium</span> were normal or enhanced compared to controls . 