Glucagon-induced desensitization of broiler adipocyte lipolysis.

Continuous exposure of cells to a hormonal stimulus results in attenuation of the hormone's effects on the cell; a process known as desensitization. The present study was undertaken to determine whether glucagon (GLU) induces desensitization of its lipolytic effect in adipocytes isolated from the abdominal fat of market-age broilers. Preincubation of adipocytes with 10 to 100 ng/mL of porcine GLU (pGLU) or chicken GLU (cGLU) for 24 h reduced (P less than .05) GLU-stimulated lipolysis. However, pGLU decreased (P less than .05) lipolysis to a greater extent than cGLU. Maximal lipolysis was reduced 70% by pGLU and 55% by cGLU. Chicken GLU also exhibited lower biological potency for acutely stimulating lipolysis from control and cGLU-treated adipocytes. Glycerol release from control adipocytes incubated for 1 h with .3 ng/mL of cGLU or pGLU was 26 and 42 nmol/h per 3% cells, respectively. The GLU-induced decrease in lipolysis occurred rapidly and was partially reversible. The results of the present study indicated that GLU induced desensitization of its lipolytic effect in broiler adipocytes.