Both GRF/GHRH and GHRP-2 (but not GHRP-6) cause PKC translocation and GH release in sheep pituitary cells, with PKC inhibition blocking both pathways.
GHRP-2 uses PKC; GHRP-6 doesn'tGHRP-2 and GRF require PKC translocation for GH release, while GHRP-6 bypasses this requirement
What the researchers found
GRF and GHRP-2 both require PKC translocation for GH release, while GHRP-6 releases GH through a PKC-independent mechanism in ovine somatotrophs.
Why it matters
Understanding the signaling differences between GHRPs explains their different clinical profiles and informs rational drug design.
How the study worked
Cultured sheep somatotrophs treated with GRF, GHRP-2, or GHRP-6. PKC translocation (cytosol to membrane) and GH release measured with and without PKC inhibitors.
What this study cannot tell us
In vitro ovine pituitary cells; may differ from human tissue. Only one PKC inhibitor tested.
How to read the evidence
Moderate in vitro evidence from ovine pituitary cells with clear mechanistic distinction.
When this study was published
Published in 1997, furthering understanding of distinct GHRP signaling mechanisms.
The bigger picture
This study further clarified the distinct signaling mechanisms of different GH secretagogues, explaining why GHRP-2 is more potent than GHRP-6.
Questions still open
- Does GHRP-2's PKC dependence explain its greater potency over GHRP-6?
- Could PKC pathway enhancement further increase GHRP-2's GH-releasing effect?
Common questions
What is PKC translocation?
Why do GHRP-2 and GHRP-6 use different signaling?
Read the original research
The role of protein kinase C in GH secretion induced by GH-releasing factor and GH-releasing peptides in cultured ovine somatotrophs.
The Journal of endocrinology, 154(2), 219-30
Citation
Wu, D; Clarke, I J; Chen, C. (1997). The role of protein kinase C in GH secretion induced by GH-releasing factor and GH-releasing peptides in cultured ovine somatotrophs.. The Journal of endocrinology, 154(2), 219-30.