Mukaddam-Daher S, Gutkowska J, Tremblay J, Dam T V, Quillen E W
Department of Obstetrics and Gynecology, McGill University, Montreal, Quebec, Canada.
Endocrinology. 1995 Oct;136(10):4565-71. doi: 10.1210/endo.136.10.7664678.
These studies were designed to characterize the atrial natriuretic peptide (ANF) receptor subtypes (guanylyl cyclase GC-A and GC-B and ANF-C) in normal sheep kidneys and to evaluate alterations in receptor kinetics during pregnancy. Kidneys were obtained from 12 nonpregnant and 12 pregnant sheep during late gestation and maintained on a 100 mmol/day salt intake. Competition binding receptor assays using [125I]human ANF showed that inner medullary membranes are exclusively of the GC-A subtype. The maximum binding capacity (Bmax, 109 +/- 12 vs. 89 +/- 18 fmol/mg protein) and dissociation constant (Kd, 240 +/- 70 vs. 324 +/- 99 pM) are not altered by pregnancy. Specific binding of glomerular membranes to [125I]Tyr-C-type natriuretic peptide, which shows the highest affinity toward GC-B receptors, was observed, but this binding was abolished when ANF-C receptors were saturated with excess C-ANF-(101-121), suggesting that [125I]Tyr-C-type natriuretic peptide binding was mediated by ANF-C receptors. Binding of [125I]human ANF to glomerular membranes revealed that glomerular ANF receptor number was reduced during pregnancy (1040 +/- 212 vs. 335 +/- 42 fmol/mg protein; P = 0.001), but binding affinity was not changed. The reduced number was mainly due to a decrease in ANF-C receptor density (832 +/- 213 vs. 260 +/- 31 fmol/mg protein; P = 0.005). Autoradiography of whole kidney frozen sections produced similar findings. These studies demonstrate that GC-B receptors are absent from renal glomeruli and inner medulla, and that ANF receptor subtypes are differentially regulated in the pregnant sheep kidney, suggesting a role for ANF in the altered volume and pressure homeostasis of pregnancy.
这些研究旨在表征正常绵羊肾脏中的心房利钠肽（ANF）受体亚型（鸟苷酸环化酶GC-A和GC-B以及ANF-C），并评估妊娠期间受体动力学的变化。在妊娠后期从12只未怀孕和12只怀孕的绵羊获取肾脏，并维持每日100 mmol的盐摄入量。使用[125I]人ANF的竞争结合受体分析表明，髓质内膜仅为GC-A亚型。妊娠不会改变最大结合容量（Bmax，109±12对89±18 fmol/mg蛋白质）和解离常数（Kd，240±70对324±99 pM）。观察到肾小球膜与[125I]酪氨酸-C型利钠肽的特异性结合，其对GC-B受体具有最高亲和力，但当ANF-C受体被过量的C-ANF-（101-121）饱和时，这种结合被消除，表明[125I]酪氨酸-C型利钠肽结合是由ANF-C受体介导的。[125I]人ANF与肾小球膜的结合显示，妊娠期间肾小球ANF受体数量减少（1040±212对335±42 fmol/mg蛋白质；P = 0.001），但结合亲和力未改变。数量减少主要是由于ANF-C受体密度降低（832±213对260±31 fmol/mg蛋白质；P = 0.005）。全肾冰冻切片的放射自显影产生了类似的结果。这些研究表明，肾小球和髓质内不存在GC-B受体，并且在怀孕绵羊肾脏中ANF受体亚型受到不同调节，提示ANF在妊娠期间改变的容量和压力稳态中起作用。
