Intracellular pathways of receptor-bound GnRH agonist in pituitary gonadotropes.
Localization of GnRH receptors in rat pituitary gonadotropes was studied by use of 125I-[azidobenzoyl-D-Lys6]GnRH which, upon photolysis, is covalently bound to the receptor molecule. Using high resolution autoradiography, it was found that, after a 90-min incubation of the analog with pituitary cells at 4 degrees C, 93% of the silver grains were associated with the plasma membrane of the gonadotropes. After 45-min incubation of the cells at 37 degrees C, clustering and internalization of the receptor-bound GnRH analog were evident. Silver grains were associated with coated pits, intracellular vesicles, Golgi complexes, lysosome-like structures and secretory granules. The data indicate that receptor-bound GnRH agonist is internalized, at least in part, via coated pits and is subsequently routed to lysosomes where degradation of the hormone-receptor complex may occur. The presence of a considerable amount of silver grains associated with secretory granules may suggest that some of the internalized receptor molecules can escape degradation and be recycled to the cell membrane.
Hazum
E
E
Koch
Y
Y
Liscovitch
M
M
Amsterdam
A
A
D000818:Animals; D001345:Autoradiography; D003034:Coated Pits, Cell-Membrane / Q000378:metabolism; D003594:Cytoplasmic Granules / Q000378:metabolism; D005260:Female; D013007:Growth Hormone-Releasing Hormone / Q000378:metabolism*; D008247:Lysosomes / Q000378:metabolism; D008854:Microscopy, Electron; D010902:Pituitary Gland / Q000378:metabolism* / Q000648:ultrastructure; D051381:Rats; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011966:Receptors, LHRH
D011956:Receptors, Cell Surface; D011966:Receptors, LHRH; D013007:Growth Hormone-Releasing Hormone