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: At puberty ( P40 ) , half the PCPA - treated rats and half the saline - treated rats began treatment with testosterone ( T , 5 mg / kg , 5 days / week ) .
### Output Text:
At puberty ( P40 ) , half the <span class="chemical">PCPA</span> - treated rats and half the saline - treated rats began treatment with <span class="chemical">testosterone</span> ( <span class="chemical">T</span> , 5 mg / kg , 5 days / week ) . 