Pituitary synaptic protein SNAP-25 sensitive to GnRH is necessary for LH release

Objective: The protein SNAP-25 is located in the plasma membrane and is known to participate in hormone exocytosis process. In the present work we studied the role of SNAP-25 on LH secretion in permeabilized adenohypophyseal cultured cells. The question of whether GnRH regulates SNAP-25 expression in adenohypophyseal cultured cells and in the adenohypophyses in vivo was also investigated.

Methods: In digitonin-permeabilized cells incubated with anti-SNAP-25, stimulated LH secretion with Ca2+ was analysed. The presence and expression of SNAP-25 in adenohypophyseal cultured cells incubated with GnRH and in adenohypophyses of orchidectomized rats with GnRH administration was studied by immunochemistry and immunoblotting.

Results: Immunochemical study revealed that SNAP-25 was present in cultured adenohypophyseal cells and in adenohypophysis of orchidectomized rats both with GnRH treatment. We found that LH secretion can be blocked by antibodies raised against SNAP-25 in permeabilized cells. Likewise, GnRH administration induced a significant decrease of SNAP-25 expression in cultured adenohypophyseal cells and in adenohypophysis of orchidectomized rats.

Conclusion: Our study showed that SNAP-25 is present in adenohypophyses in vitro as well as in vivo and that is involved in LH release and that GnRH can modify its expression.