Conversion of [125I]growth hormone into high molecular weight forms in vivo

[125I]-growth hormone, injected in rats, was converted into high molecular weight forms (70,000 to over 200,000 daltons) as judged by gel filtration of blood serum samples collected after the injection. These forms were reactive with antisera against growth hormone, although their immunoreactivity was only 50% of that of control, single component [125I]growth hormone. Their molecular weight was not affected significantly by denaturation with sodium dodecyl sulfate. Incubation of [125I]growth hormone with blood serum in vitro did not result in the production of high molecular weight forms.