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: Therefore , it is suggested that the administration of PS enhances the toxicity of AMNS on the glomerulus and readily produces progressive FSGS in rats resulting in the end - stage renal disease .
### Output Text:
Therefore , it is suggested that the administration of <span class="chemical">PS</span> enhances the toxicity of <span class="chemical">AMNS</span> on the glomerulus and readily produces progressive FSGS in rats resulting in the end - stage renal disease . 