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: Upregulation of brain expression of P - glycoprotein in MRP2 - deficient TR ( - ) rats resembles seizure - induced up - regulation of this drug efflux transporter in normal rats .
### Output Text:
Upregulation of brain expression of P - glycoprotein in MRP2 - deficient TR ( - ) rats resembles seizure - induced up - regulation of this drug efflux transporter in normal rats . 