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 assess the molecular basis of disturbances in transmembraneous transport of Na + , we studied the response of cardiac ( Na , K ) - ATPase to NO - deficient hypertension induced in rats by NO - synthase inhibition with 40 mg / kg / day N ( G ) - nitro - L - arginine methyl ester ( L - NAME ) for 4 four weeks .
### Output Text:
To assess the molecular basis of disturbances in transmembraneous transport of <span class="chemical">Na</span> + , we studied the response of cardiac ( <span class="chemical">Na</span> , <span class="chemical">K</span> ) - ATPase to <span class="chemical">NO</span> - deficient hypertension induced in rats by <span class="chemical">NO</span> - synthase inhibition with 40 mg / kg / day <span class="chemical">N ( G ) - nitro - L - arginine methyl ester</span> ( <span class="chemical">L - NAME</span> ) for 4 four weeks . 