Effects of growth hormone administration on neurotensin release in children with growth delay

Neurotensin (NT), a tridecapeptide originally isolated from bovine hypothalamus, has numerous actions on endocrine functions. Since intravenous injection of NT in the rat stimulated the release of growth hormone (GH) among several pituitary hormones, the aim of our study was to investigate in humans the effects of GH injection on NT plasma levels. Plasma samples were obtained from 13 children with growth delay (7 boys and 6 girls; age range 5 years 1 month-14 years 1 month; mean +/- SE 10 years 9 months +/- 7 months) to evaluate NT and GH values before treatment and 4, 12 and 24 h after a subcutaneous rhGH injection (0.15 IU/kg). Plasma was extracted on a SEP-PAC C18 column and NT was eluted with propanol. NT concentrations were measured by a specific RIA and expressed as fmol/ml plasma. GH (ng/ml) and somatomedin C (SMC; U/ml) were evaluated by RIA using commercial kits. Free fatty acids (FFA; mEq/l) were measured using a colorimetric peroxidase technique. Before GH administration, NT levels were 7.19 +/- 1.01 fmol/ml. A significant increase in NT values was found 4 h (36.5 +/- 9.62, p < 0.001), 12 h (40.85 +/- 6.64, p < 0.001) and 24 h (19.5 +/- 3.48, p < 0.05) after GH injection. This increase was significantly correlated with the circulating GH levels 4 h after GH administration and with the circulating SMC levels 24 h after GH administration. No correlation was found between NT and FFA values.(ABSTRACT TRUNCATED AT 250 WORDS)