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: Vasopressin plays a major role in the pathogenesis of DOCA - salt hypertension , since the elevation of blood pressure was not substantial in the rats with lithium - treated diabetes insipidus after DOCA - salt treatment .
### Output Text:
<span class="chemical">Vasopressin</span> plays a major role in the pathogenesis of <span class="chemical">DOCA</span> - salt hypertension , since the elevation of blood pressure was not substantial in the rats with <span class="chemical">lithium</span> - treated diabetes insipidus after <span class="chemical">DOCA</span> - salt treatment . 