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 purpose of the present study was to determine if prenatal dexamethasone programmed a progressive increase in blood pressure and renal injury in rats .
### Output Text:
The purpose of the present study was to determine if prenatal <span class="chemical">dexamethasone</span> programmed a progressive increase in blood pressure and renal injury in rats . 