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: Contribution of the sympathetic nervous system to salt - sensitivity in lifetime captopril - treated spontaneously hypertensive rats .
### Output Text:
Contribution of the sympathetic nervous system to salt - sensitivity in lifetime <span class="chemical">captopril</span> - treated spontaneously hypertensive rats . 