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: They all exhibited markedly reduced plasma catecholamines and plasma renin activity in both recumbent and upright positions and had marked hypersensitivity to the pressor effects of infused norepinephrine .
### Output Text:
They all exhibited markedly reduced plasma <span class="chemical">catecholamines</span> and plasma renin activity in both recumbent and upright positions and had marked hypersensitivity to the pressor effects of infused <span class="chemical">norepinephrine</span> . 