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: When activating the ( Na , K ) - ATPase with its substrate ATP , no changes in Km and Vmax values were observed in NO - deficient rats .
### Output Text:
When activating the ( <span class="chemical">Na</span> , <span class="chemical">K</span> ) - ATPase with its substrate <span class="chemical">ATP</span> , no changes in Km and Vmax values were observed in <span class="chemical">NO</span> - deficient rats . 