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: HS diet for 4 wk increased renal cortical angiotensinogen mRNA and protein only in male DS , which was prevented by castration .
### Output Text:
HS diet for 4 wk increased renal cortical angiotensinogen mRNA and protein only in male DS , which was prevented by castration . 