title: Localization and quantification of angiotensin II (A II) binding sites in the kidney of Xenopus laevis--lack of A II receptors in the adrenal tissue.
abstract: The distribution and properties of angiotensin binding sites in the kidney of the clawed toad Xenopus laevis were studied using quantitative in vitro autoradiography. Specific binding sites for [125I]-[Val5]-angiotensin II (A II) were located in the glomeruli of the kidney but not in the adrenal tissue. [125I]-[Val5]-A II binding was equilibrated after 45 min. Scatchard and Hill analyses of saturation experiments showed that [125I]-[Val5]-A II binds to a single class of binding sites with a dissociation constant (Kd) of 1.884 +/- 0.535 nM and a maximum binding capacity (Bmax) of 0.484 +/- 0.144 fmol/mm2 (n = 8). Various angiotensin analogues displaced [125I]-[Val5]-A II in the rank order [Sar1, Ile5]-A II greater than human A II greater than [125I]-[Val5]-A II = [Val5]-A II = human A III much greater than human A I. Unrelated peptides did not alter the binding of [125I]-[Val5]-A II. Acclimation to 1.5% seawater increased [125I]-[Val5]-A II binding in glomeruli after 12 hr but returned to control levels after 7 days. Steroidogenic and catecholaminergic actions of [Val5]-A II on the adrenal tissue were examined in vitro and in vivo. Compared with known interrenal stimulators [human ACTH(1-39) and AVT] minimal effects were obtained only in vitro with high doses of [Val5]-A II while catecholamine release was unaffected. In vivo a single injection of 3 nmol [Val5]-A II per 100 g body wt did not change serum levels of corticosterone, aldosterone, epinephrine, norepinephrine, or dopamine.
authors.affiliation: Department of Zoology, The University, Karlsruhe, Germany.
authors.forename: W
authors.initials: W
authors.lastname: Kloas
authors.forename: W
authors.initials: W
authors.lastname: Hanke
mesh_terms: D000305:Adrenal Cortex Hormones / Q000097:blood; D000311:Adrenal Glands / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D000804:Angiotensin II / Q000032:analysis* / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001345:Autoradiography; D002395:Catecholamines / Q000097:blood; D004305:Dose-Response Relationship, Drug; D007457:Iodine Radioisotopes; D007668:Kidney / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D011945:Receptors, Angiotensin / Q000032:analysis* / Q000378:metabolism; D014982:Xenopus laevis / Q000378:metabolism*
chemical_list: D000305:Adrenal Cortex Hormones; D002395:Catecholamines; D007457:Iodine Radioisotopes; D011945:Receptors, Angiotensin; D000804:Angiotensin II