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: Acute insulin treatment normalizes the resistance to the cardiotoxic effect of isoproterenol in streptozotocin diabetic rats .
### Output Text:
Acute insulin treatment normalizes the resistance to the cardiotoxic effect of <span class="chemical">isoproterenol</span> in <span class="chemical">streptozotocin</span> diabetic rats . 