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: CCB was measured before and after administration of either vehicle , AVP , ANP , or both peptides together .
### Output Text:
CCB was measured before and after administration of either vehicle , <span class="chemical">AVP</span> , ANP , or both peptides together . 