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: Administration of GM at 40 mg / kg sc for 13 days to rats induced a significant reduction in renal blood flow ( RBF ) and inulin clearance ( CIn ) as well as marked tubular damage .
### Output Text:
Administration of <span class="chemical">GM</span> at 40 mg / kg sc for 13 days to rats induced a significant reduction in renal blood flow ( RBF ) and inulin clearance ( CIn ) as well as marked tubular damage . 