Studies on angiotensin II receptors

Cox, Helen Mary (1982) Studies on angiotensin II receptors. University of Southampton, Doctoral Thesis.

Abstract

The location of 1251-AII binding sites was investigated in rat intestinal and renal cortex membranes using classical radiolabelled hormone-receptor binding assays. High affinity, specific 125I-AII binding sites were identified in renal cortex crude basolateral and brush-border membranes with a hD of 0.62 t 0.11nM and Bmax of 303.78 t 33.90fmol/mg. In contrast, no specific 1251-AII binding was found with membranes from intestinal epithelia. Specific 125I-AII binding to renal cortex membranes was partially dependent on Ila+, maximal binding being achieved with 130aud Hat Absence of ::aCl reduced steady state binding and increased the rate of ligand dissociation converting a proportion of sites to a lower affinity. Guanine nucleotides directly decreased specific binding with an order of potency; Gpp(IdH)p > GTP >i ITP > GDP > ATP > GI•P > IDP. Gpp(I!H)p reduced steady state binding and decreased ligand dissociation which resulted in an increased binding affinity. 1' I-AII specific binding was sensitive to DTT in a concentration dependent manner. Protection against DTT inactivation was afforded by preincubating membranes with unlabelled AIL The absence of MaUl from preincubations with DTT also reduced the rate of inactivation. Rates of 1251-AII association and dissociation were affected by DTT in a complex manner, converting a proportion of sites to a higher affinity. Guanine nucleotides reduced specific 1251-AII binding synergistically with DTT. These studies have therefore tentatively identified a cation sensitive site in the vicinity of the renal cortex epithelial 1251-AII binding site. Interaction of the former with :Ca+ is proposed to alter the binding site conformation, enabling maximal specific 1251-AII binding and in the absence of labelled hormone, exrosing a disulfide bond to allow a more rapid rate of inactivation by DTT.

This record has no associated files available for download.

Contributors

Download statistics