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

Author(s)

Peroni, Cibele N. ; Hayashida, Cesar Y. ; Nascimento, Nancy ; Longuini, Viviane C. ; Toledo, Rodrigo A. ; Bartolini, Paolo ; Bowers, Cyril Y. ; Toledo, Sergio P. A.

• Document type: Journal article
• Source: Clinics; v. 67, n. 3, p. 8-pg., 2012-01-01.

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/litmice, which represent a model of GH deficiency arising frommutated 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. (AU)

• FAPESP's process: 09/15386-6 - Analysis of the CDKN1A, CDKN1B, CDKN2B and CDKN2C genes in multiple endocrine neoplasias type 1 and 2.
• Grantee: Rodrigo de Almeida Toledo
• Support Opportunities: Scholarships in Brazil - Post-Doctoral