Mesotocin receptor binding in oviduct uterus of the hen before and after oviposition.
[(125)I]mesotocin (MT) binding of membrane fractions of the oviduct uterus in laying hens and nonlaying hens was measured by the use of radioligand binding assay to elucidate the presence of MT receptor in the uterine tissue, and whether the binding to the receptor changes before and after oviposition. The uterine tissue of the hen was found to contain a specific [(125)I]MT binding component having properties of MT receptor (i.e., binding specificity, saturable binding, high affinity, and limited capacity). The equilibrium dissociation constant (K(d)) was 0.46 +/- 0.05 nM (x +/- SEM; n = 4) in laying hens holding a hard-shelled egg in the uterus (shell gland) and 0.78 +/- 0.02 nM (n = 4) in nonlaying hens. The maximum binding capacity (B(max)) was 0.28 +/- 0.03 pmol/mg of protein (n = 4) in laying hens and 0.19 +/- 0.01 pmol/mg of protein (n = 4) in nonlaying hens. The K(d) value of the laying hens varied from 0.37 to 0.91 nM during an oviposition cycle showing a decrease 30 min before oviposition and an increase 4 h after oviposition. The B(max) value also varied from 0.15 to 0.38 pmol/mg of protein showing an increase 3 h before oviposition, a decrease 30 min before oviposition, and an increase 4 h after oviposition. In the nonlaying hen, both values were almost constant during a 24-h day. The changes in the binding affinity and capacity of MT receptor of the uterus may be related to oviposition in the hen.
Takahashi
T
T
Department of Biological Diversity and Resources, Gifu University, Yanagido, Gifu 501-1193, Japan.
Kawashima
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M
D000818:Animals; D001667:Binding, Competitive; D002645:Chickens / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005260:Female; D007457:Iodine Radioisotopes; D007700:Kinetics; D010057:Oviducts / Q000737:chemistry / Q000378:metabolism*; D010058:Oviposition / Q000502:physiology*; D011979:Receptors, Pituitary Hormone / Q000378:metabolism*
D007457:Iodine Radioisotopes; D011979:Receptors, Pituitary Hormone; C116046:mesotocin receptor