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: To better understand the utility of GLEPP1 as a marker of glomerular injury , the amount and distribution of GLEPP1 protein and mRNA were examined by immunohistochemistry , Western blot and RNase protection assay in a model of podocyte injury in the rat .
### Output Text:
To better understand the utility of GLEPP1 as a marker of glomerular injury , the amount and distribution of GLEPP1 protein and mRNA were examined by immunohistochemistry , Western blot and RNase protection assay in a model of podocyte injury in the rat . 