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: The amounts of alphaENaC , betaENaC and gammaENaC proteins were not increased during PAN - induced sodium retention .
### Output Text:
The amounts of alphaENaC , betaENaC and gammaENaC proteins were not increased during <span class="chemical">PAN</span> - induced <span class="chemical">sodium</span> retention . 