Ability of growth hormone fragments to complete with 125I-iodinated human growth hormone for specific binding to isolated adipocytes of hypophysectomized rats.

Several noncovalent complexes of large fragments of human GH, which are less active than native human GH in stimulating glucose metabolism in adipose tissue of hypophysectomized rats, were tested for their ability to compete with 125I-iodinated human GH for specific binding to isolated adipocytes of hypophysectomized rats. The complexes tested were A (residues 1-134 + residues 141-191; S-carbamidomethylated), B (residues 1-134 + residues 135-191; S-carbamidomethylated) and C (residues 1-134 + residues 135-191; S-carboxymethylated). When compared to native human GH, the complexes were less active in competing with 125I-iodinated human GH for specific binding to adipocytes, and their order of potency in the binding assay (A greater than B greater than C) was similar to that of their respective activities in stimulating glucose metabolism in isolated adipose tissue of hypophysectomized rats.