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: Nitroprusside - induced hypotension evokes ACTH secretion which is primarily mediated by enhanced secretion of immunoreactive corticotropin - releasing factor ( irCRF ) into the hypophysial - portal circulation .
### Output Text:
<span class="chemical">Nitroprusside</span> - induced hypotension evokes ACTH secretion which is primarily mediated by enhanced secretion of immunoreactive corticotropin - releasing factor ( irCRF ) into the hypophysial - portal circulation . 