Specific binding of human growth hormone but not insulin-like growth factors by human adipocytes

Binding of human GH (hGH) and insulin-like growth factors I and II (IGFI and II) to isolated human adipocytes from adult subjects was studied. Binding equilibrium for hGH at 24 degrees C was reached at 120 min and half-maximal specific binding at 6-8 ng/ml. Apparent Ka was 2.1 X 10(9) M-1 and Bmax 7.3 X 10(-11) M/10(6) cells. The human fat cell growth hormone receptor recognized neither bovine, ovine or rat GH nor human prolactin or placental lactogen. No specific receptors for human IGFII could be demonstrated. Thus, human adipocytes do not possess IGF receptors but have specific GH receptors which recognize hGH but not GH from lower species.