title: Vasopressin, angiotensin and adrenergic receptors of rat liver Golgi fractions--molecular weight of the angiotensin-receptor irreversible complex after in vitro and in vivo labelling.
abstract: The binding of vasopressin, angiotensin II and prazosin (alpha 1-adrenergic antagonist) to purified heavy (GH) and (intermediate + light) (GI + L) rat liver Golgi fractions was studied. The three types of ligands showed a saturable and specific binding in Golgi fractions; the maximal specific binding of [3H]vasopressin, [3H]prazosin and [125I]Sar-N3-Phe-angiotensin II was respectively 5-10%, 20-30% and 30-40% of that detected in purified plasma membranes. The apparent binding affinities of the three ligands were the same whether determined in Golgi fractions or plasma membranes. The presence of vasopressin, alpha 1-adrenergic and angiotensin receptors in very different proportions, as compared to the amount of receptor detected in plasma membranes, in GH and GI + L Golgi fractions was not compatible with the idea that a plasma membrane impurity accounted for the detection of receptor in the purified intracellular particulate fractions. In vivo injection of [125I]Sar-N3-Phe-angiotensin II resulted in a receptor-mediated endocytosis of the iodo-angiotensin analog into the GH and GI + L Golgi fractions. The apparent molecular weight of the irreversible complex, [125I]angiotensin-receptor, was estimated in subcellular fractions using SDS-PAGE electrophoresis. This value was identical after either in vivo or in vitro labelling (MW = 63,000) and was indistinguishable from the molecular weight of the irreversible hormone receptor complex present in the plasma membranes.
mesh_terms: D000804:Angiotensin II / Q000031:analogs & derivatives / Q000378:metabolism; D000818:Animals; D001127:Arginine Vasopressin / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism*; D007425:Intracellular Membranes / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008970:Molecular Weight; D011224:Prazosin / Q000378:metabolism; D051381:Rats; D011941:Receptors, Adrenergic / Q000378:metabolism*; D011945:Receptors, Angiotensin / Q000378:metabolism*; D017483:Receptors, Vasopressin; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: D011941:Receptors, Adrenergic; D011945:Receptors, Angiotensin; D017483:Receptors, Vasopressin; D000804:Angiotensin II; D001127:Arginine Vasopressin; D011224:Prazosin