Effects of deflazacort and cortisone on body growth, thymus weight and gene expression of growth-related proteins in the rat.

Deflazacort is an oxazoline derivative of cortisone with presumably less serious side effects, but its effects on growth factors are unknown. The present experiments in Long Evans rats were carried out to investigate how deflazacort administration affected the growing rat, especially in relation to hepatic insulin-like growth factor I (IGF-I) and growth hormone receptor (GHR) messenger ribonucleic acid (mRNA). Four groups of animals were used: those treated with cortisone, with two different doses of deflazacort and with vehicle. Subcutaneous injections were given daily for 8 days. Thymus weight was reduced in all treated groups, with a comparable magnitude of reduction in the groups treated with cortisone and the higher dose of deflazacort (DF1). Daily weight gain was reduced significantly after cortisone treatment, but less so in the DF1 rats. Liver IFG-I and GHR mRNA were lower in the cortisone and deflazacort than in controls. However, GHR mRNA was reduced significantly only by cortisone and not by DF1. We conclude that growth failure is less severe in the DF1 rats compared to cortisone rats, which corresponds to the reduction in hepatic GHR mRNA.