title: Angiotensin receptors from rat liver, brain and pituitary gland. Expression of two subtypes in Xenopus oocytes.
abstract: Xenopus laevis oocytes were used to express angiotensin receptors encoded by mRNAs extracted from rat liver, adenohypophysis and brain. Groups of ten mRNA-injected oocytes were loaded with 45Ca2+ and the responsiveness to angiotensin II (A II) and related molecules tested by monitoring 45Ca2+ outflux. A II and angiotensin III (A III) induced a marked and transient increase in 45Ca2+ outflux from mRNA, but not from control, water-injected, oocytes. The increase over basal value of 45Ca2+ outflux during a 5 min application period of A II or A III was used as a response index. Observed responses were of high magnitude, reproducible and dose-dependent. For these reasons, mRNA-injected oocytes constitute a valuable system for investigating the pharmacological properties of angiotensin receptors from tissues of different origin under experimental conditions which eliminate tissue-specific interference which might be encountered in classical binding studies on acellular preparations. We demonstrate a fairly good parallelism between the relative potencies of A I, A II and A III in eliciting an increase in 45Ca2+ outflux from liver and adenohypophyseal mRNA-injected oocytes and the relative affinities of these peptides for binding to liver or adenohypophyseal membranes (A II greater than A III much greater than A I). The predominant receptor subtype expressed by brain mRNA discriminated very poorly between A II and A III, whereas angiotensin receptors expressed by liver or adenohypophyseal mRNA discriminated between AII and AIII very efficiently.
authors.affiliation: Centre CNRS-INSERM de Pharmacologie-Endocrinologie, Montpellier, France.
authors.forename: B
authors.initials: B
authors.lastname: Cantau
authors.forename: S
authors.initials: S
authors.lastname: Bartolami
authors.forename: P P
authors.initials: PP
authors.lastname: Baskevitch
authors.forename: F
authors.initials: F
authors.lastname: Desarnaud
authors.forename: D
authors.initials: D
authors.lastname: Chicot
authors.forename: S
authors.initials: S
authors.lastname: Jard
mesh_terms: D000809:Angiotensins / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000378:metabolism*; D002118:Calcium / Q000502:physiology; D003001:Cloning, Molecular; D066298:In Vitro Techniques; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism; D010902:Pituitary Gland / Q000378:metabolism*; D011945:Receptors, Angiotensin / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D012504:Saralasin / Q000494:pharmacology; D014982:Xenopus laevis
chemical_list: D000809:Angiotensins; D011945:Receptors, Angiotensin; D012504:Saralasin; D002118:Calcium