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: Renal catecholamine stores and stimulus - induced overflow in the vehicle - treated group consisted of norepinephrine only .
### Output Text:
Renal <span class="chemical">catecholamine</span> stores and stimulus - induced overflow in the vehicle - treated group consisted of <span class="chemical">norepinephrine</span> only . 