EFFECTS OF ENDOTOXIN LIPOPOLYSACCHARIDE ADMINISTRATION ON THE SOMATOTROPIC AXIS

The aim of this work was to study the effect of chronic activation of the immune system on the somatotropic axis. Accordingly, the changes i n growth hormone (GH) secretion, circulating insulin-like growth facto r-I (IGF-I) and IGF binding proteins (IGFBPs) in response to endotoxin lipopolysaccharide (LPS) administration were examined in adult male W istar rats. Acute LPS injection (2.5, 25 or 250 mu g/kg) increased ser um corticosterone in a dose-dependent manner and decreased serum level s of insulin and IGF-I, serum GH concentration declined linearly as th e LPS dose increased. Western ligand blot showed an increase in the 33 kDa band (corresponding to IGFBP-1 and IGFBP-2) in the rats that rece ived the highest dose of LPS (250 mu g/kg). Chronic LPS administration (250 mu g/kg daily for 8 days) significantly decreased body weight, s erum levels of IGF-I and pituitary GH content, whereas it increased ci rculating IGFBP-3 (47 kDa band), IGFBP-1 and IGFBP-2 (33 kDa band) and the 24 kDa band (which possibly corresponds to IGFBP-4). Serum concen tration of corticosterone and hypothalamic somatostatin content were a lso increased by chronic LPS treatment. These data suggest that the de crease in GH and IGF-I secretion and the increase in circulating IGFBP s are important mechanisms in body weight loss during chronic inflamma tion.