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 concluded that dietary sodium restriction increases diuretic - induced potassium loss , presumably by an increased activity of the renin - angiotensin - aldosterone system , while sodium delivery to the distal renal tubules remains sufficiently high to allow increased potassium secretion .
### Output Text:
It is concluded that dietary <span class="chemical">sodium</span> restriction increases diuretic - induced <span class="chemical">potassium</span> loss , presumably by an increased activity of the renin - <span class="chemical">angiotensin</span> - <span class="chemical">aldosterone</span> system , while <span class="chemical">sodium</span> delivery to the distal renal tubules remains sufficiently high to allow increased <span class="chemical">potassium</span> secretion . 