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: After recovery from hypertension , the activity of ( Na , K ) - ATPase increased , due to higher affinity of the ATP - binding site , as revealed from the lowered Km value for ATP .
### Output Text:
After recovery from hypertension , the activity of ( <span class="chemical">Na</span> , <span class="chemical">K</span> ) - ATPase increased , due to higher affinity of the <span class="chemical">ATP</span> - binding site , as revealed from the lowered Km value for <span class="chemical">ATP</span> . 