title: Stimulation of the angiotensin II type I receptor on bovine adrenal glomerulosa cells activates a temperature-sensitive internalization-recycling pathway.
abstract: Angiotensin II (Ang II) is an important regulator of aldosterone production by bovine adrenal glomerulosa cells. On these cells Ang II interacts with the AT1 receptor that is coupled to a G protein controlling the activity of phospholipase C. A primary culture of bovine adrenal glomerulosa cells was used to study the internalization-recycling mechanism of the AT1 receptor after stimulation with Ang II. When cells were pretreated with 10 nM Ang II for 30 min at 37 degrees C and binding studies were performed at 12 degrees C we observed a 48% loss in [125I]Ang II binding. Scatchard analysis revealed that this loss in binding translated into a decreased affinity of the AT1 receptor without any loss in the total amount of binding sites. Under the same conditions an important internalization of [125I]Ang II was invariably observed. These observations suggest that a mechanism was at work to recycle the internalized receptors to the cell surface during the binding studies. Following internalization we indeed observed an externalization of [125I]Ang II. This phenomenon relatively rapid at 37 degrees C was much slower at 12 degrees C and completely inhibited at 4 degrees C. When cells were pretreated with 10 nM Ang II for 30 min at 37 degrees C binding assays at 4 degrees C no longer revealed a loss of binding affinity but rather a 54% reduction in the total amount of binding sites. The maximal binding capacity could be recovered during incubations at 12 degrees C. These results reveal the existence of a dynamic recycling process for the AT1 receptor. In accordance with this interpretation the phenomenon was blocked by monensin, a known inhibitor of receptor recycling. These studies suggest that the stimulation of the AT1 receptor sets in motion an internalization-recycling process that seems to be a fundamental aspect of the AT1 receptor transduction mechanism.
authors.affiliation: Department of Pharmacology, Faculty of Medicine, Université de Sherbrooke, Quebec, Canada.
authors.forename: D E
authors.initials: DE
authors.lastname: Richard
authors.forename: L
authors.initials: L
authors.lastname: Chrétien
authors.forename: M
authors.initials: M
authors.lastname: Caron
authors.forename: G
authors.initials: G
authors.lastname: Guillemette
mesh_terms: D000804:Angiotensin II / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D002417:Cattle; D003500:Cyclization; D005455:Fluorescent Antibody Technique; D008985:Monensin / Q000494:pharmacology; D011945:Receptors, Angiotensin / Q000187:drug effects* / Q000378:metabolism; D013696:Temperature; D015384:Zona Glomerulosa / Q000187:drug effects* / Q000378:metabolism
chemical_list: D011945:Receptors, Angiotensin; D000804:Angiotensin II; D008985:Monensin