Characteristics of pharmacokinetics, distribution and excretion of recombinant human interleukin-3 in mice

Concentration-time profiles of 125I-labelled recombinant human interleukin-3 (125I-rhIL-3) were determined by reverse phase high performance liquid chromatography (RHPLC) after subcutaneous administration of the drug 90 μg/kg in mice. The elimination T1/2 in plasma was 1.73 h. Rapid biodegradation was found in plasma. The distribution profiles of total radioactivity were as follows: The highest level was found in urinary system. Levels in bile-enteric system, lymph nodes, bone marrow and spleen approximated that in plasma, and level in brain was the lowest. A total of (84.0 +- 9.2)% of the injected dose was excreted through urine and feces within 48 h, of which (71.9 +- 6.7)% through urine and (12.2 +- 5.3)% through feces. The RHPLC analysis revealed that kidney was one of the major organ for biodegradation