2368
Cells were separated from blood samples on a Ficoll gradient and incubated with different concentrations of [3H]testosterone in the presence or absence of a 400-fold excess of unlabelled testosterone .
 None
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: cell line, protein, RNA, DNA, cell type 
Text: {0} 
Answer:
 None