Kidney as an important metabolic organ for recombinant human insulin-like growth factor-I

To investigate the kidney as a metabolic organ of recombinant human insulin-like growth factor-I (rhIGF-I), a single chain polypeptide consisting of 70 amino acids, the renal extraction and urinary excretion of rhIGF-I were examined in rats. The distribution of rhIGF-I after subcutaneous administration and the degradation in various tissue homogenates were also studied to evaluate the contributions of the other tissues to its metabolism. Although potent enzymes capable of degrading rhIGF-I exist in other tissues, no other organ except the kidney seemed to play a specific role in clearing rhIGF-I from the systemic circulation.