an improved method for the analysis of retinoids in mouse plasma allows quantification of all-trans-retinoic acid ( ra ) and n- ( 2-hydroxyethyl ) retinamide ( nhera ) in amounts as low as 2 ng/ml ( 7 x 10 ( -9 ) m ) , the approximate endogenous concentration of ra .
C0035339
retinoids
C0040845
ra