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 , DMTU significantly reduced the tubular damage and lipid peroxidation , but it did not affect renal hemodynamics and vasoactive substances .
### Output Text:
In contrast , <span class="chemical">DMTU</span> significantly reduced the tubular damage and lipid peroxidation , but it did not affect renal hemodynamics and vasoactive substances . 