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: These findings suggest that disruption of the blood - brain barrier during acute hypertension is not related to the synthesis / release of bradykinin to activate B2 receptors .
### Output Text:
These findings suggest that disruption of the blood - brain barrier during acute hypertension is not related to the synthesis / release of <span class="chemical">bradykinin</span> to activate B2 receptors . 