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: In contrast , a significant decline in glomerular filtration rate was found after the introduction of suprofen to the kidney perfused with uric acid ; no changes were found with suprofen in the absence of uric acid .
### Output Text:
In contrast , a significant decline in glomerular filtration rate was found after the introduction of <span class="chemical">suprofen</span> to the kidney perfused with <span class="chemical">uric acid</span> ; no changes were found with <span class="chemical">suprofen</span> in the absence of <span class="chemical">uric acid</span> . 