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Growth hormone response to growth hormone-releasing peptide-2 in growth hormone-deficient little mice.

Peroni CN, Hayashida CY, Nascimento N, Longuini VC, Toledo RA, Bartolini P, Bowers CY, Toledo SP - Clinics (Sao Paulo) (2012)

Bottom Line: To investigate a possible direct, growth hormone-releasing, hormone-independent action of a growth hormone secretagogue, GHRP-2, in pituitary somatotroph cells in the presence of inactive growth hormone-releasing hormone receptors.Here, we have demonstrated that lit/lit mice, which harbor a germline mutation in the Growth hormone-releasing hormone gene, maintain a limited but statistically significant growth hormone elevation after exogenous stimulation with GHRP-2.The present data probably reflect a direct, growth hormone-independent effect on Growth hormone S (ghrelin) stimulation in the remaining pituitary somatotrophs of little mice that is mediated by growth hormone S-R 1a.

View Article: PubMed Central - PubMed

Affiliation: Biotechnology Department, National Nuclear Energy Commission, Cidade Universitária, São Paulo, SP, Brazil.

ABSTRACT

Objective: To investigate a possible direct, growth hormone-releasing, hormone-independent action of a growth hormone secretagogue, GHRP-2, in pituitary somatotroph cells in the presence of inactive growth hormone-releasing hormone receptors.

Materials and methods: The responses of serum growth hormone to acutely injected growth hormone-releasing P-2 in lit/lit mice, which represent a model of GH deficiency arising from mutated growth hormone-releasing hormone-receptors, were compared to those observed in the heterozygous (lit/+) littermates and wild-type (+/+) C57BL/6J mice.

Results: After the administration of 10 mcg of growth hormone-releasing P-2 to lit/lit mice, a growth hormone release of 9.3±1.5 ng/ml was observed compared with 1.04±1.15 ng/ml in controls (p<0.001). In comparison, an intermediate growth hormone release of 34.5±9.7 ng/ml and a higher growth hormone release of 163±46 ng/ml were induced in the lit/+ mice and wild-type mice, respectively. Thus, GHRP-2 stimulated growth hormone in the lit/lit mice, and the release of growth hormone in vivo may be only partially dependent on growth hormone-releasing hormone. Additionally, the plasma leptin and ghrelin levels were evaluated in the lit/lit mice under basal and stimulated conditions.

Conclusions: Here, we have demonstrated that lit/lit mice, which harbor a germline mutation in the Growth hormone-releasing hormone gene, maintain a limited but statistically significant growth hormone elevation after exogenous stimulation with GHRP-2. The present data probably reflect a direct, growth hormone-independent effect on Growth hormone S (ghrelin) stimulation in the remaining pituitary somatotrophs of little mice that is mediated by growth hormone S-R 1a.

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Related in: MedlinePlus

Mouse GH (mGH) serum concentrations were determined by a sensitive RIA method (detection limit, 0.25 ng/ml). Shown here are the mGH increases after the acute administration of 10 µg GHRP-2 in lit/lit, lit/+ and +/+ mice as well as the saline injection of lit/lit mice. Three animals were used for each time point only once each and then sacrificed. In total, 18 animals were used for each of the four observations, and 72 animals were used in total.
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f2-cln_67p265: Mouse GH (mGH) serum concentrations were determined by a sensitive RIA method (detection limit, 0.25 ng/ml). Shown here are the mGH increases after the acute administration of 10 µg GHRP-2 in lit/lit, lit/+ and +/+ mice as well as the saline injection of lit/lit mice. Three animals were used for each time point only once each and then sacrificed. In total, 18 animals were used for each of the four observations, and 72 animals were used in total.

Mentions: The mean peak GH response in the control group (+/+) was 163 ng/ml, and it occurred 10 min after the administration of GHRP-2 with a 24-fold increase over the baseline levels (Figure 2). In the lit/+ and lit/lit mice, there was a significant GH response to GHRP-2 at 5-10 min. Twenty minutes after GHRP-2 injection, GH levels returned to the baseline values.


Growth hormone response to growth hormone-releasing peptide-2 in growth hormone-deficient little mice.

Peroni CN, Hayashida CY, Nascimento N, Longuini VC, Toledo RA, Bartolini P, Bowers CY, Toledo SP - Clinics (Sao Paulo) (2012)

Mouse GH (mGH) serum concentrations were determined by a sensitive RIA method (detection limit, 0.25 ng/ml). Shown here are the mGH increases after the acute administration of 10 µg GHRP-2 in lit/lit, lit/+ and +/+ mice as well as the saline injection of lit/lit mice. Three animals were used for each time point only once each and then sacrificed. In total, 18 animals were used for each of the four observations, and 72 animals were used in total.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3297037&req=5

f2-cln_67p265: Mouse GH (mGH) serum concentrations were determined by a sensitive RIA method (detection limit, 0.25 ng/ml). Shown here are the mGH increases after the acute administration of 10 µg GHRP-2 in lit/lit, lit/+ and +/+ mice as well as the saline injection of lit/lit mice. Three animals were used for each time point only once each and then sacrificed. In total, 18 animals were used for each of the four observations, and 72 animals were used in total.
Mentions: The mean peak GH response in the control group (+/+) was 163 ng/ml, and it occurred 10 min after the administration of GHRP-2 with a 24-fold increase over the baseline levels (Figure 2). In the lit/+ and lit/lit mice, there was a significant GH response to GHRP-2 at 5-10 min. Twenty minutes after GHRP-2 injection, GH levels returned to the baseline values.

Bottom Line: To investigate a possible direct, growth hormone-releasing, hormone-independent action of a growth hormone secretagogue, GHRP-2, in pituitary somatotroph cells in the presence of inactive growth hormone-releasing hormone receptors.Here, we have demonstrated that lit/lit mice, which harbor a germline mutation in the Growth hormone-releasing hormone gene, maintain a limited but statistically significant growth hormone elevation after exogenous stimulation with GHRP-2.The present data probably reflect a direct, growth hormone-independent effect on Growth hormone S (ghrelin) stimulation in the remaining pituitary somatotrophs of little mice that is mediated by growth hormone S-R 1a.

View Article: PubMed Central - PubMed

Affiliation: Biotechnology Department, National Nuclear Energy Commission, Cidade Universitária, São Paulo, SP, Brazil.

ABSTRACT

Objective: To investigate a possible direct, growth hormone-releasing, hormone-independent action of a growth hormone secretagogue, GHRP-2, in pituitary somatotroph cells in the presence of inactive growth hormone-releasing hormone receptors.

Materials and methods: The responses of serum growth hormone to acutely injected growth hormone-releasing P-2 in lit/lit mice, which represent a model of GH deficiency arising from mutated growth hormone-releasing hormone-receptors, were compared to those observed in the heterozygous (lit/+) littermates and wild-type (+/+) C57BL/6J mice.

Results: After the administration of 10 mcg of growth hormone-releasing P-2 to lit/lit mice, a growth hormone release of 9.3±1.5 ng/ml was observed compared with 1.04±1.15 ng/ml in controls (p<0.001). In comparison, an intermediate growth hormone release of 34.5±9.7 ng/ml and a higher growth hormone release of 163±46 ng/ml were induced in the lit/+ mice and wild-type mice, respectively. Thus, GHRP-2 stimulated growth hormone in the lit/lit mice, and the release of growth hormone in vivo may be only partially dependent on growth hormone-releasing hormone. Additionally, the plasma leptin and ghrelin levels were evaluated in the lit/lit mice under basal and stimulated conditions.

Conclusions: Here, we have demonstrated that lit/lit mice, which harbor a germline mutation in the Growth hormone-releasing hormone gene, maintain a limited but statistically significant growth hormone elevation after exogenous stimulation with GHRP-2. The present data probably reflect a direct, growth hormone-independent effect on Growth hormone S (ghrelin) stimulation in the remaining pituitary somatotrophs of little mice that is mediated by growth hormone S-R 1a.

Show MeSH
Related in: MedlinePlus