Ghrelin and GHRP-6 boost growth hormone release from pituitary cells by increasing the number of functional sodium channels, revealing a new piece of the GH secretion puzzle.
GH release abolishedBlocking sodium channels with tetrodotoxin completely prevented ghrelin- and GHRP-6-induced growth hormone release
What the researchers found
Chronic treatment with ghrelin and its synthetic analog GHRP-6 significantly increases growth hormone release from bovine pituitary somatotropes, associated with an increase in Na+ macroscopic current. This effect is abolished by tetrodotoxin, indicating involvement of TTX-sensitive Na+ channels NaV1.1 and NaV1.2, whose transcript levels are upregulated by ghrelin and GHRP-6.
Why it matters
Understanding how ghrelin regulates growth hormone secretion via sodium channels can help develop new treatments for growth disorders and improve knowledge of pituitary cell function.
How the study worked
The study used cultured bovine pituitary somatotropes treated chronically with ghrelin and GHRP-6. Growth hormone release was measured alongside electrophysiological recordings of Na+ currents. RT-PCR was performed to assess mRNA levels of GH and sodium channel isoforms. Sodium channel blockade was tested using tetrodotoxin.
What this study cannot tell us
The study was conducted in cultured bovine cells, which may not fully replicate human physiology. The exact signaling pathways linking ghrelin to sodium channel expression were not detailed.
How to read the evidence
This is a basic science study using cultured bovine pituitary cells. While it provides mechanistic insights with well-controlled experiments, findings from animal cell cultures require validation in human systems before clinical conclusions can be drawn.
When this study was published
Published in 2015, this study remains relevant as foundational research explaining how ghrelin peptides control growth hormone release at the ion channel level. The mechanisms described have not been superseded.
The bigger picture
Growth hormone releasing peptides like GHRP-6 are widely discussed in the peptide community, but the exact cellular mechanisms by which they trigger GH release are still being mapped. This study adds an important piece: sodium channels in pituitary cells are not just passive bystanders but active participants that ghrelin upregulates to drive hormone secretion. This could inform the development of more targeted GH-releasing therapeutics.
Questions still open
- Do these sodium channel changes also occur in human pituitary cells, or is this specific to bovine tissue?
- Could drugs targeting NaV1.1 or NaV1.2 channels be used to modulate growth hormone release therapeutically?
- What intracellular signaling pathways connect ghrelin receptor activation to sodium channel gene upregulation?
Common questions
What are somatotropes and why do they matter?
Why does it matter that sodium channels are involved in growth hormone release?
Read the original research
Ghrelin increases growth hormone production and functional expression of NaV1.1 and Na V1.2 channels in pituitary somatotropes.
Endocrine, 48(3), 929-36
Citation
Magdaleno-Méndez, Adasue; Domínguez, Belisario; Rodríguez-Andrade, Araceli; Barrientos-Morales, Manuel; Cervantes-Acosta, Patricia; Hernández-Beltrán, Antonio; González-Ramírez, Ricardo; Felix, Ricardo. (2015). Ghrelin increases growth hormone production and functional expression of NaV1.1 and Na V1.2 channels in pituitary somatotropes.. Endocrine, 48(3), 929-36. https://doi.org/10.1007/s12020-014-0392-x