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 effects of i . v . bolus administration of cromakalim ( 1 - 10 micrograms / kg ) and pinacidil ( 3 - 100 micrograms / kg ) on large ( circumflex artery ) and small coronary arteries and on systemic hemodynamics were investigated in chronically instrumented conscious dogs and compared to those of nitroglycerin ( 0 . 03 - 10 micrograms / kg ) .
### Output Text:
The effects of i . v . bolus administration of <span class="chemical">cromakalim</span> ( 1 - 10 micrograms / kg ) and <span class="chemical">pinacidil</span> ( 3 - 100 micrograms / kg ) on large ( circumflex artery ) and small coronary arteries and on systemic hemodynamics were investigated in chronically instrumented conscious dogs and compared to those of <span class="chemical">nitroglycerin</span> ( 0 . 03 - 10 micrograms / kg ) . 