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: We examined the abundance of ENaC subunit mRNAs and proteins in puromycin aminonucleoside ( PAN ) - induced nephrotic syndrome .
### Output Text:
We examined the abundance of ENaC subunit mRNAs and proteins in <span class="chemical">puromycin aminonucleoside</span> ( <span class="chemical">PAN</span> ) - induced nephrotic syndrome . 