Sex differences in the pharmacokinetics of recombinant human granulocyte colony-stimulating factor in the rat

The pharmacokinetics of recombinant human granulocyte colony-stimulating factor (rhG-CSF) were studied in male and female rats. The serum concentration of rhG-CSF after iv and sc administration to male and female Sprague-Dawley rats at a dose of 5 and 100 micrograms/kg was investigated by a sandwich enzyme-linked immunosorbent assay. After iv administration, AUC and half-lives of rhG-CSF in female rats were smaller than those for male rats. The volume of distribution of rhG-CSF in female rats was not significantly different from that in male rats. After sc administration, AUC, mean residence time, and half-lives of elimination phase in female rats were smaller than those for male rats. The in vitro biological activities of rhG-CSF were investigated using [3H]thymidine uptake assay in cultures of bone marrow cells obtained from male and female rat femur. Female rat bone marrow cells showed a similar dose-response profile to rhG-CSF to that of male rat bone marrow cells. The effect of rhG-CSF administration in rats was a specific activity on the neutrophil lineage with an increase of neutrophils in peripheral blood. The in vivo effects of rhG-CSF after iv and sc administration to male and female rats at 5 and 100 micrograms/kg doses were determined. After 100 micrograms/kg administration, the neutrophil count in female rats was similar to that in male rats in the early period; however, the neutrophil count in female rats was lower than that in male rats 24 hr after administration.(ABSTRACT TRUNCATED AT 250 WORDS)