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: Our case supports the hypothesis that endogenous renal prostaglandins play a role in the maintenance of renal blood flow when circulating plasma volume is diminished .
### Output Text:
Our case supports the hypothesis that endogenous renal <span class="chemical">prostaglandins</span> play a role in the maintenance of renal blood flow when circulating plasma volume is diminished . 