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: Thus , " stress " levels of adrenaline ( 230 pg / ml ) for 6 h cause a delayed and protracted pressor effect .
### Output Text:
Thus , " stress " levels of <span class="chemical">adrenaline</span> ( 230 pg / ml ) for 6 h cause a delayed and protracted pressor effect . 