Open Access

ARTICLE

Prolactin-releasing activity of GHRP-5 (Momany peptide) on lactotrophs in vivo and in vitro

ANA LUCÍA DE PAUL^*, MÓNICA BONATERRA^*, CLAUDIA GABRIELA PELLIZAS^**, AGUSTÍN AOKI^*, ALICIA INÉS TORRES^*

* Centro de Microscopía Electrónica. Facultad de Ciencias Médicas.
** Departamento de Bioquímica Clínica, Facultad de Ciencias Químicas. Universidad Nacional de Córdoba. RA 5000. CC362. Córdoba, República Argentina.

Corresponding Author: Alicia Inés Torres, Tel/Fax: (+54-351) 433 3021; E-mail:

BIOCELL 2002, 26(1), 49-60. https://doi.org/10.32604/biocell.2002.26.049

Abstract

In the present study the in vivo and in vitro effects of GHRP-5 on the PRL-releasing activity in correlation with the morphological changes of lactotroph cells and their transcriptional activity were evaluated. The in vitro treatment (12 µg/100g BW/day for 3 days) of male rats with GHRP-5 does not induce any significant changes in serum PRL levels. In contrast, the addition of GHRP-5 to pituitary cell cultures increased significantly the release of PRL. This effect is enhanced in cell cultures of enriched lactotrophs, increasing significantly the secretion of PRL, the concentrations of which were 50% higher than that of untreated control cells. The administration of GHRP-5 provokes several changes in the fine structure of lactotrophs, compatible with an increased secretory activity. After the GHRP-5 treatment the different lactotroph subtypes persist but the subtype I displaying secretory granules of larger size (500-900nm) and a significant development of the Golgi apparatus and RER were more frequently observed. These results can be correlated with a significant augmentation in PRL mRNA after the GHRP-5 treatment. In spite of that no variations in serum PRL levels were observed in vitro, following GHRP-5 treatment, the lactotroph population experienced evident fine structure modifications, concordant with an upsurge of PRL synthesis. These observations confirmed a direct action of GHRP-5 on receptors expressed by lactotrophs. The differential actions of GHRP-5 on on vitro and in vitro designs confirm a different effectiveness of this secretagogue to induce PRL secretion.

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