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 effects of progesterone treatment on bupivacaine arrhythmogenicity in beating rat heart myocyte cultures and on anesthetized rats were determined .
### Output Text:
The effects of <span class="chemical">progesterone</span> treatment on <span class="chemical">bupivacaine</span> arrhythmogenicity in beating rat heart myocyte cultures and on anesthetized rats were determined . 