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: While contractions to carbachol and ATP were the same in inflamed and in control strips when related to a reference potassium response , isoprenaline - induced relaxations were smaller in inflamed strips .
### Output Text:
While contractions to <span class="chemical">carbachol</span> and <span class="chemical">ATP</span> were the same in inflamed and in control strips when related to a reference <span class="chemical">potassium</span> response , <span class="chemical">isoprenaline</span> - induced relaxations were smaller in inflamed strips . 