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: Intraplatelet cAMP content was gradually but significantly increased to 9 . 84 + / - 4 . 59 pmol per 10 ( 9 ) platelets at day 14 in comparison with the initial value ( 6 . 87 + / - 2 . 25 pmol ) .
### Output Text:
Intraplatelet <span class="chemical">cAMP</span> content was gradually but significantly increased to 9 . 84 + / - 4 . 59 pmol per 10 ( 9 ) platelets at day 14 in comparison with the initial value ( 6 . 87 + / - 2 . 25 pmol ) . 