title: Monoiodinated angiotensin II is a potent, full agonist analog of angiotensin II.
abstract: Mono 125I-angiotensin II (Ang II) has been used extensively as a radioligand to identify Ang II receptors whereas its receptor binding properties are well characterized, its biological activity has been less well studied. To examine this issue, nonradioisotopic monoiodo-Ang II was prepared and compared to Ang II. Monoiodo-Ang II was found to be a potent, full agonist in in vivo bioassays and a more potent (2.5-fold) pressor agent than the native hormone Ang II in the pithed rat. In eliciting dipsogenic responses monoiodo-Ang II was equipotent to Ang II, but was less potent (2.7-fold) than Ang II in contracting rat aortic strips. These results suggest that the well characterized binding affinity of monoiodo-Ang II is representative of its biological activity (40-250% of the activity of Ang II). The variation in relative peptide potency is consistent with the hypothesis of a heterogeneity of Ang II receptors. Most importantly, the similar efficacies between Ang II and monoiodo-Ang II indicate that the monoiodinated Ang II is a suitable ligand for the study of Ang II receptors.
mesh_terms: D000804:Angiotensin II / Q000031:analogs & derivatives*; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D007457:Iodine Radioisotopes; D007553:Isotope Labeling; D008433:Mathematics; D051381:Rats; D011945:Receptors, Angiotensin / Q000378:metabolism
chemical_list: D007457:Iodine Radioisotopes; D011945:Receptors, Angiotensin; D000804:Angiotensin II