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: Urinary sodium excretion reached signficantly lower values in sgk1 ( + / + ) mice ( 15 + / - 5 mumol / mg crea ) than in sgk1 ( - / - ) mice ( 35 + / - 5 mumol / mg crea ) and was associated with a significantly higher body weight gain in sgk1 ( + / + ) compared with sgk1 ( - / - ) mice ( + 6 . 6 + / - 0 . 7 vs . + 4 . 1 + / - 0 . 8 g ) .
### Output Text:
Urinary <span class="chemical">sodium</span> excretion reached signficantly lower values in sgk1 ( + / + ) mice ( 15 + / - 5 mumol / mg crea ) than in sgk1 ( - / - ) mice ( 35 + / - 5 mumol / mg crea ) and was associated with a significantly higher body weight gain in sgk1 ( + / + ) compared with sgk1 ( - / - ) mice ( + 6 . 6 + / - 0 . 7 vs . + 4 . 1 + / - 0 . 8 g ) . 