HUMAN GROWTH-HORMONE VARIANT PRODUCES INSULIN-LIKE AND LIPOLYTIC RESPONSES IN RAT ADIPOSE-TISSUE

Genes for normal human pituitary GH (hGH-N) and the GH variant (hGH-V) were expressed in stably transfected mouse mammary cells. The biological properties of hGH-N and hGH-V secreted into the medium were examined using rat adipocytes or epididymal fat segments. Methionyl-hGH produced in E. coli served as a reference standard. The three preparations were quite similar in their ability to bind specifically to intact fat cells and were virtually indistinguishable in their ability to increase glucose oxidation (an insulin-like response), induce refractoriness to insulin-like stimulation, and induce lipolysis in the presence of glucocorticoid. We conclude that placentally expressed hGH-V has a spectrum of metabolic activity comparable to pituitary hGH-N and may contribute to regulation of carbohydrate and lipid metabolism during pregnancy.