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: Mechanistic studies revealed that OB rats are sensitized due to : ( 1 ) higher oxyradical stress leading to upregulation of uncoupling proteins 2 and 3 , ( 2 ) downregulation of cardiac peroxisome proliferators activated receptor - alpha , ( 3 ) decreased plasma adiponectin levels , ( 4 ) decreased cardiac fatty - acid oxidation ( 666 . 9 + / - 14 . 0 nmol / min / g heart in ND versus 400 . 2 + / - 11 . 8 nmol / min / g heart in OB ) , ( 5 ) decreased mitochondrial AMP - alpha2 protein kinase , and ( 6 ) 86 % drop in cardiac ATP levels accompanied by decreased ATP / ADP ratio after doxorubicin administration .
### Output Text:
Mechanistic studies revealed that OB rats are sensitized due to : ( 1 ) higher oxyradical stress leading to upregulation of uncoupling proteins 2 and 3 , ( 2 ) downregulation of cardiac peroxisome proliferators activated receptor - alpha , ( 3 ) decreased plasma adiponectin levels , ( 4 ) decreased cardiac fatty - acid oxidation ( 666 . 9 + / - 14 . 0 nmol / min / g heart in ND versus 400 . 2 + / - 11 . 8 nmol / min / g heart in OB ) , ( 5 ) decreased mitochondrial <span class="chemical">AMP</span> - alpha2 protein kinase , and ( 6 ) 86 % drop in cardiac <span class="chemical">ATP</span> levels accompanied by decreased <span class="chemical">ATP</span> / <span class="chemical">ADP</span> ratio after <span class="chemical">doxorubicin</span> administration . 