Mesotocin binding to receptors in hen kidney plasma membranes.
Radioligand assays were performed to demonstrate the presence of a receptor for mesotocin (MT) in the membrane fractions of the kidney of the hen. Specific [125I]MT bindings were decreased by the presence of Mg2+ and Ca2+, increased by the presence of EDTA, increased during the first 4 h of incubation and then reached a plateau, and increased with the increase in the protein concentration from 2.5 to 20 micrograms. The membrane fraction showed binding specificity to [125I]MT. The Scatchard plot revealed a curvilinear profile that indicated the presence of two classes of binding sites: a high affinity site and a low affinity site. The equilibrium dissociation constant was 0.08 +/- 0.01 nM (mean +/- SEM; n = 5) in the high affinity site and 0.87 +/- 0.08 nM (n = 5) in the low affinity site. The maximum binding capacity of the high and low affinity sites was 42 +/- 4 and 129 +/- 6 fmol/mg protein, respectively. The results suggest the presence of two distinct MT receptors in the kidney of the hen.
Takahashi
T
T
Department of Animal Science and Technology, Gifu University, Japan.
Kawashima
M
M
Yasuoka
T
T
Kamiyoshi
M
M
Tanaka
K
K
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002462:Cell Membrane / Q000737:chemistry / Q000648:ultrastructure; D002645:Chickens / Q000378:metabolism*; D005260:Female; D007457:Iodine Radioisotopes; D007668:Kidney / Q000737:chemistry* / Q000166:cytology* / Q000648:ultrastructure; D008274:Magnesium / Q000494:pharmacology; D008565:Membrane Proteins / Q000032:analysis; D010121:Oxytocin / Q000031:analogs & derivatives* / Q000378:metabolism; D011869:Radioligand Assay; D011956:Receptors, Cell Surface / Q000032:analysis* / Q000378:metabolism*; D013696:Temperature; D013997:Time Factors
D007457:Iodine Radioisotopes; D008565:Membrane Proteins; D011956:Receptors, Cell Surface; C001713:mesotocin; D010121:Oxytocin; D008274:Magnesium; D002118:Calcium