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: After starting PGE1 or TMP , MAP and rate pressure product ( RPP ) decreased significantly compared with preinfusion values ( P < 0 . 01 ) , and the degree of hypotension due to PGE1 remained constant until 60 min after its discontinuation .
### Output Text:
After starting <span class="chemical">PGE1</span> or <span class="chemical">TMP</span> , MAP and rate pressure product ( RPP ) decreased significantly compared with preinfusion values ( P < 0 . 01 ) , and the degree of hypotension due to <span class="chemical">PGE1</span> remained constant until 60 min after its discontinuation . 