1124
The expression levels of human RAR alpha ( hRAR alpha, receptor for all-trans RA ) and the human retinoid-X receptor alpha ( hRXR alpha receptor for 9-cis RA ) were determined by Northern blot analysis.
 ( protein: hRXR alpha receptor, None) , ( protein: hRAR alpha, receptor, None) , ( protein: human RAR alpha, None) , ( protein: human retinoid-X receptor alpha, None) 
Locate the role in the text that participated in the event based on the event type and return it in the event list. 
 Option: Event type: RNA,cell type,protein,cell line,DNA, Arguments type: . 
Text: {0} 
Answer:
 ( protein: hRXR alpha receptor, None) , ( protein: hRAR alpha, receptor, None) , ( protein: human RAR alpha, None) , ( protein: human retinoid-X receptor alpha, None) 