GROWTH-HORMONE AND GROWTH-HORMONE BINDING-PROTEIN IN HUMAN URINE

The presence of growth hormone binding protein (GH-BP) in urine was demonstrated in normal subjects. Scatchard analysis showed that an association constant (Ka) and a maximum binding capacity (Bmax) of urinary GH-BP were 2.3 ± 0.8 × 108 M-1 and 19.2 ± 4.0 ng/mg urinary protein, respectively. The molecular weight of the urinary GH-BP was estimated to be 50000 to 70000 on gel chromatography. Although the molecular weight and Ka were similar to those of plasma GH-BP, Bmax of urinary GH-BP was significantly higher than that of plasma GH-BP (0.44 ± 0.12 ng/mg protein). GH-BP in urine may be derived from plasma and/or renal tubules.