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: Taking into account that the sarcolemmal integrity is stabilized by the dystrophin - glycoprotein complex ( DGC ) that connects actin and laminin in contractile machinery and extracellular matrix and by integrins , this study tests the hypothesis that isoproterenol affects sarcolemmal stability through changes in the DGC and integrins .
### Output Text:
Taking into account that the sarcolemmal integrity is stabilized by the dystrophin - glycoprotein complex ( DGC ) that connects actin and laminin in contractile machinery and extracellular matrix and by integrins , this study tests the hypothesis that <span class="chemical">isoproterenol</span> affects sarcolemmal stability through changes in the DGC and integrins . 