Changes in serum insulin-like growth factor binding protein-2, -3, and -6 levels in patients with chronic renal failure following renal transplantation.

The pathophysiological roles of insulin-like growth factor binding protein (IGFBP)-6 have not been elucidated. Recently, we measured serum IGFBP-6 by Western immunoblot (WIB) and have found that serum IGFBP-6 levels increased in patients with chronic renal failure (CRF). In the present study, serum IGFBP-6 levels were measured in 10 patients with CRF before and 1, 7 and 14 days after renal transplantation to investigate further clinical significance and regulation of serum IGFBP-6. IGFBP-2 and -3 levels, usually elevated in patients with CRF, were also measured after renal transplantation. Serum IGFBP-2 and -6 levels from patients with CRF by Western immunoblot increased to 230+/-90% (mean +/- SD), and 400+/-110% of the reference serum, respectively, and these levels did not change after hemodialysis. Serum IGFBP-6 levels decreased to 47+/-20% of the basal level 1 day after renal transplantation, and the IGFBP-6 levels in two patients whose renal function worsened again due to rejection increased to more than 60% of the basal levels on the 14th day. In contrast to IGFBP-6, serum IGFBP-2 levels did not decrease during the 14 days after renal transplantation in all patients. Serum IGFBP-3 levels were significantly higher in CRF than normal sera (5.5+/-1.2 vs 3.7+/-0.5 microg/ml, P < 0.01), and the levels decreased to the normal range (2.7+/-1.0 microg/ml) within 1 day after the transplantation, whereas the levels increased again in one of two patients with poorly-functioning graft. In addition, we demonstrated IGFBP-6 in urine from normal adults. These results indicate that IGFBP-6 might be excreted by the kidneys and serum IGFBP-3 and -6 levels might be related with renal function, and that the regulation of serum IGFBP-2 levels differs from those of IGFBP-3 and -6.