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: In contrast , in normal - salt rats creatinine clearance was decreased but to a lesser extent at week 2 and 3 , and in salt - loaded rats creatinine clearance did not change for 2 weeks and was decreased by 43 % at week 3 .
### Output Text:
In contrast , in normal - salt rats <span class="chemical">creatinine</span> clearance was decreased but to a lesser extent at week 2 and 3 , and in salt - loaded rats <span class="chemical">creatinine</span> clearance did not change for 2 weeks and was decreased by 43 % at week 3 . 