GROWTH-HORMONE ADMINISTRATION CAN IMPROVE GROWTH IN GLUCOCORTICOID-INJECTED RATS WITHOUT AFFECTING THE LYMPHOCYTOPENIC EFFECT OF THE GLUCOCORTICOID

Long-term glucocorticoid therapy as it is found in children with kidne y transplants results in retarded longitudinal growth. The aim of the present study was to evaluate if growth hormone could improve longitud inal growth in glucocorticoid-injected experimental animals without af fecting the immune-suppressive effect of the glucocorticoid. 117 femal e Wistar rats were injected from the ages of 2-5 months with either sa line, growth hormone (5 mg/kg/day), or glucocorticoid (methylprednisol one 1,3,6 or 9 mg/kg/day), alone or in combination with growth hormone (5 mg/kg/day). Body weight, nose-tail length and length of the lower extremity were measured continuously during the study. After death, fe moral and tibial lengths, growth at the proximal, epiphyseal growth pl ate, muscle mass and immunological parameters were examined. Glucocort icoid administration dose-dependently decreased weight gain and growth (nose-tail length, growth of the lower extremity), lengths of femur a nd tibia, growth at the proximal, epiphyseal growth plate and muscle m ass. Glucocorticoid administration decreased spleen and thymus weight as well as the white blood cell count (WBC count), mainly due to a dec rease in lymphocyte number. For all glucocorticoid doses examined, gro wth hormone increased weight gain and growth (nose-tail length, growth of the lower extremity), lengths of femur and tibia, and muscle mass. The effects of growth hormone were, however, dose-dependently decreas ed by glucocorticoid administration. Growth hormone injection alone in creased the WBC count due to an increase in the number of lymphocytes and monocytes. When the two hormones were administered concomitantly, growth hormone did not, however, reverse the lymphocytopenic effect in duced by glucocorticoid administration. In conclusion, growth hormone can increase longitudinal growth and increase muscle mass in glucocort icoid-injected rats, if a glucocorticoid preparation of a short half-l ife is used. Growth hormone does not reverse the lymphocytopenic effec t of glucocorticoid injections. (C) 1998 Churchill Livingstone.