Growth hormone and insulin binding to isolated hepatocytes in the genetically dwarf mouse

Abstract

The interaction of growth hormone with its specific receptors in dwarf mice was investigated. (1) The interaction of 125I-labeled human growth hormone with isolated mouse liver cells is a specific, time-dependent and saturable process. Hepataocytes of male and female dw/dw mice bound only 10-20% as much growth hormone per unit of cell surface area as those of their litter mates. Scatchard analysis suggested that this decrease in binding was due to a decreased number of receptor sites in th liver cell of the dwarf mouse. (2) In contrast to the marked decrease in growth hormone receptors, the binding of insulin is higher in dwarf mice than in litter mates, at low hormone concentration. (3) Competition and stoichiometric studies indicate that growth hormone and prolactin bind to the same type of binding site in female and male mouse hepatocytes. These results indicate that dwarfism in this animal was associated with a loss in the number of growth hormone binding sites. The decrease in growth hormone receptors and the increase in insulin receptors correlate well with the respective biological activity of these two hormones.