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: The greater LV hypertrophy in TGR rats was associated with more pronounced downregulation of beta - AR and upregulation of LV beta - AR kinase - 1 mRNA levels compared with those in SD rats .
### Output Text:
The greater LV hypertrophy in TGR rats was associated with more pronounced downregulation of beta - AR and upregulation of LV beta - AR kinase - 1 mRNA levels compared with those in SD rats . 