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: To clarify the effects of bromocriptine on prolactinoma cells in vivo , immunohistochemical , ultrastructural and morphometrical analyses were applied to estrogen - induced rat prolactinoma cells 1 h and 6 h after injection of bromocriptine ( 3 mg / kg of body weight ) .
### Output Text:
To clarify the effects of <span class="chemical">bromocriptine</span> on prolactinoma cells in vivo , immunohistochemical , ultrastructural and morphometrical analyses were applied to <span class="chemical">estrogen</span> - induced rat prolactinoma cells 1 h and 6 h after injection of <span class="chemical">bromocriptine</span> ( 3 mg / kg of body weight ) . 