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 conclusion , administration of isoproterenol to rats results in primary loss of dystrophin , the most sensitive among the structural proteins that form the DGC that connects the extracellular matrix and the cytoskeleton in cardiomyocyte .
### Output Text:
In conclusion , administration of <span class="chemical">isoproterenol</span> to rats results in primary loss of dystrophin , the most sensitive among the structural proteins that form the DGC that connects the extracellular matrix and the cytoskeleton in cardiomyocyte . 