Expression of the Short Isoform of the Growth Hormone Receptor in Adipocytes

Abstract

Growth hormone (GH) acts on a variety of terminally differentiated cells, including adipocytes, myocytes, hepatocytes, and pancreatic beta cells, to regulate energy balance (1). In adipocytes GH produces an immediate insulin-like response that is most readily demonstrated by accelerated glucose metabolism in cells that have been deprived of GH for at least 3 h (2) and a delayed anti-insulin-like response typified by increased lipolysis (3). Because these responses are independently affected by chemical modifications of GH (4, 5) or the GH receptor (6), it was suggested that different responses may require different hormone receptor interactions (5, 6). However, consistent findings of linear Scatchard isotherms argue for a single class of binding sites (6–9). In the absence of any definitive mechanism for how GH might produce any of its biological actions, the question of whether GH interacts with a single receptor or a variety of receptor complexes cannot yet be answered.