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: It is not known why this effect occurred in some individuals but not in others , but our results indicate a correlation between aldosterone production and this renal effect of L - dopa .
### Output Text:
It is not known why this effect occurred in some individuals but not in others , but our results indicate a correlation between <span class="chemical">aldosterone</span> production and this renal effect of <span class="chemical">L - dopa</span> . 