The individual role played by GH and IGF-I in the regulation of hypothalamic GHRH and SRIF gene expression is still object of debate. We have investigated the effect of exogenously administered recombinant hGH (rhGH) and recombinant hIGF-I (rhIGF-I) in ad libitum fed control and starved rats, the latter an animal model which is characterized by low circulating levels of endogenous GH and IGF-I. Adult male rats were fed ad libitum (C) or food-deprived (S) for 72 hours; rats in either C or S groups were treated with systemic administration of rhGH and rhIGF-I for 3 days. GHRH, SRIF and GH mRNA levels were evaluated by Northern and slot blot hybridization. Administration of rhGH (250 micrograms/kg/twice daily, sc) induced a significant inhibition of GHRH and a significant stimulation of SRIF mRNA levels in C rats; GH treatment was, however, ineffective on both neuropeptide mRNA levels in the S group. Continuous infusion of rhIGF-I (300 micrograms/kg/day, sc) induced a significant increase of SRIF levels in both C and S rats but did not modify GHRH mRNA levels in either group. In the pituitary, GH mRNA levels followed a pattern very similar to that of GHRH. These results provide evidence for a direct role of GH in the inhibition of GHRH mRNA levels; IGF-I appears more involved in the direct stimulation of SRIF mRNA levels
Ghigo, M., Torsello, A., Grilli, R., Luoni, M., Guidi, M., Cella, S., et al. (1997). Effects of GH and IGF-I administration on GHRH and somatostatin mRNA levels: I. A study on ad libitum fed and starved adult male rats. JOURNAL OF ENDOCRINOLOGICAL INVESTIGATION, 20(3), 144-150 [10.1007/BF03346893].
Effects of GH and IGF-I administration on GHRH and somatostatin mRNA levels: I. A study on ad libitum fed and starved adult male rats
TORSELLO, ANTONIO BIAGIO;LOCATELLI, VITTORIO;
1997
Abstract
The individual role played by GH and IGF-I in the regulation of hypothalamic GHRH and SRIF gene expression is still object of debate. We have investigated the effect of exogenously administered recombinant hGH (rhGH) and recombinant hIGF-I (rhIGF-I) in ad libitum fed control and starved rats, the latter an animal model which is characterized by low circulating levels of endogenous GH and IGF-I. Adult male rats were fed ad libitum (C) or food-deprived (S) for 72 hours; rats in either C or S groups were treated with systemic administration of rhGH and rhIGF-I for 3 days. GHRH, SRIF and GH mRNA levels were evaluated by Northern and slot blot hybridization. Administration of rhGH (250 micrograms/kg/twice daily, sc) induced a significant inhibition of GHRH and a significant stimulation of SRIF mRNA levels in C rats; GH treatment was, however, ineffective on both neuropeptide mRNA levels in the S group. Continuous infusion of rhIGF-I (300 micrograms/kg/day, sc) induced a significant increase of SRIF levels in both C and S rats but did not modify GHRH mRNA levels in either group. In the pituitary, GH mRNA levels followed a pattern very similar to that of GHRH. These results provide evidence for a direct role of GH in the inhibition of GHRH mRNA levels; IGF-I appears more involved in the direct stimulation of SRIF mRNA levels
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