Microsomal protein The total protein concentration within the microsomal fraction of cells. Microsomes refer to vesicle-like artifacts reformed from pieces of endoplasmic reticulum when eukaryotic cells are broken up in a laboratory. Originally from the CUAHSI HIS VariableNameCV. See: http://his.cuahsi.org/mastercvreg/edit_cv11.aspx?tbl=VariableNameCV. ODM2 Variable Name Controlled Vocabulary ODM2 Working Group A vocabulary for describing the name of Variables.