Cbl homeostasis in male and female MRP1-deficient mice and controls. The content of Cbl in blood plasma, kidney, liver, ileum, and colon was determined in control and Mrp1^(−/−) mice. The content in plasma is shown as Cbl concentration (in nM) and in the other tissues as nanomolar Cbl per gram of tissue protein. Each measurement is the mean ± 1 SD of groups of 8 mice (4 males and 4 females). Asterisk indicates the P values less than .05 (t test) for the difference between means in the tissues.