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 isoproterenol administered rats , the level of lipid peroxides increased significantly in the serum and heart .
### Output Text:
In <span class="chemical">isoproterenol</span> administered rats , the level of lipid <span class="chemical">peroxides</span> increased significantly in the serum and heart . 