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 relative amounts of alphaENaC , betaENaC and gammaENaC mRNAs were determined in kidneys from these rats by real - time quantitative TaqMan PCR , and the amounts of proteins by Western blot .
### Output Text:
The relative amounts of alphaENaC , betaENaC and gammaENaC mRNAs were determined in kidneys from these rats by real - time quantitative TaqMan PCR , and the amounts of proteins by Western blot . 