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: Decreased Expression of Na / K - ATPase , NHE3 , NBC1 , AQP1 and OAT in Gentamicin - induced Nephropathy .
### Output Text:
Decreased Expression of <span class="chemical">Na</span> / <span class="chemical">K</span> - ATPase , NHE3 , NBC1 , AQP1 and OAT in <span class="chemical">Gentamicin</span> - induced Nephropathy . 