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: The time courses of urinary sodium excretion , plasma aldosterone concentration and proteinuria were studied in male Sprague - Dawley rats treated with a single dose of either PAN or vehicle .
### Output Text:
The time courses of urinary <span class="chemical">sodium</span> excretion , plasma <span class="chemical">aldosterone</span> concentration and proteinuria were studied in male Sprague - Dawley rats treated with a single dose of either <span class="chemical">PAN</span> or vehicle . 