These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Different effects of intermittent and continuous growth hormone (GH) administration on serum somatomedin-C/insulin-like growth factor I and liver GH receptors in hypophysectomized rats.
    Author: Maiter D, Underwood LE, Maes M, Davenport ML, Ketelslegers JM.
    Journal: Endocrinology; 1988 Aug; 123(2):1053-9. PubMed ID: 3396497.
    Abstract:
    To determine if the pattern of GH delivery is important for the regulation of serum somatomedin-C/insulin-like growth factor I (Sm-C/IGF-I) and liver somatogenic receptors, we have measured serum Sm-C/IGF-I concentrations and free (H2O-treated homogenates) and total (MgCl2-treated homogenates) liver GH-binding sites in hypophysectomized rats treated for 7 days with rat GH (rGH), given either continuously by osmotic minipumps (50 and 250 micrograms/day) or intermittently (four sc injections of 12.5 micrograms/day). At a daily dose of 50 micrograms, intermittent rGH produced greater weight gain [+29.7 +/- 0.8 g (mean +/- SE)] than continuous GH infusion (23.3 +/- 2.0 g; P less than 0.01). Likewise, the serum Sm-C/IGF-I concentration rose more with intermittent (0.33 +/- 0.1 U/ml) than with continuous delivery (0.17 +/- 0.01 U/ml; P less than 0.01). The serum Sm-C/IGF-I level achieved with repeated GH injections was even greater than that after continuous delivery of a 5-fold higher GH dose (250 micrograms/day; 0.27 +/- 0.02 U/ml; P less than 0.05). Continuous infusions of 50 and 250 micrograms rGH/day increased the number of liver total GH receptors by 2.5-fold over that of controls. In contrast, frequent GH injections did not affect GH binding, and the serum Sm-C/IGF-I concentration did not correlate with liver GH-binding sites in the GH-injected rats (r = 0.189; P = NS). Induction of hepatic PRL receptors was 10-fold higher when GH was given continuously than when it was given intermittently. The close correlation observed between GH- and PRL-binding sites in all GH-treated rats (r = 0.955; P less than 0.001) suggests that their regulation may be linked. These data suggest that the regulatory mechanism controlling Sm-C/IGF-I production and growth might be different from those that regulate GH receptor concentrations, with GH pulses being crucial for the maximal stimulation of Sm-C/IGF and growth, but continuous exposure to GH being required for up-regulation of liver GH receptors.
    [Abstract] [Full Text] [Related] [New Search]