Serradeil-Le Gal C, Raufaste D, Brossard G, Pouzet B, Marty E, Maffrand J P, Le Fur G
Sanofi Recherche, Exploratory Research Department, Toulouse, France.
FEBS Lett. 1997 Mar 10;404(2-3):185-91. doi: 10.1016/s0014-5793(97)00125-7.
Characterization and localization of leptin binding sites were investigated in rat kidneys using [125I]leptin as a ligand. [125I]Leptin specific binding was found in high amounts in rat renomedullary membranes. This binding was specific, saturable, time-dependent (K(obs) = 0.055 +/- 0.008 min(-1)) and the dissociation of receptor-bound ligand was slowly reversible (K(-1) = 0.048 +/- 0.013 min(-1)). From saturation experiments, a single class of high-affinity binding sites for leptin was identified with an apparent K(d) of 0.57 +/- 0.14 nM and a B(max) of 45 +/- 10 fmol/mg protein. [125I]Leptin binding was inhibited in a dose-dependent manner by cold leptin and was highly selective since not displaceable by a number of other hormones or peptides. Autoradiographic experiments performed on adult rat kidney sections showed the intense presence of [125I]leptin receptors only in specific areas of the renal inner medulla and also consistent labeling associated with vascular structures in the corticomedullary region. The study of the postnatal developmental expression of leptin receptors in the kidney showed very low expression during the early postnatal period (8-21 days). Full expression of leptin sites was achieved at about 30 days and remained stable throughout adulthood (60 days and upwards). Moreover, in vivo administration of leptin (0.5 mg/kg i.p.) induced a significant and rapid diuretic effect in normally hydrated conscious rats. Thus, these data constitute the first characterization and mapping of [125I]leptin specific binding sites in the rat kidney and raise the possibility of a renal control by leptin.
使用[125I]瘦素作为配体，对大鼠肾脏中的瘦素结合位点进行了表征和定位研究。在大鼠肾髓质膜中发现了大量的[125I]瘦素特异性结合。这种结合具有特异性、可饱和性、时间依赖性（K(obs)=0.055±0.008 min(-1)），且受体结合配体的解离是缓慢可逆的（K(-1)=0.048±0.013 min(-1)）。通过饱和实验，确定了一类瘦素的高亲和力结合位点，其表观K(d)为0.57±0.14 nM，B(max)为45±10 fmol/mg蛋白。冷瘦素以剂量依赖性方式抑制[125I]瘦素结合，并且具有高度选择性，因为它不会被许多其他激素或肽所取代。对成年大鼠肾脏切片进行的放射自显影实验表明，[125I]瘦素受体仅在肾内髓质的特定区域大量存在，并且在皮质髓质区域也有与血管结构相关的一致标记。对肾脏中瘦素受体出生后发育表达的研究表明，在出生后早期（8 - 21天）表达非常低。瘦素结合位点在约30天时达到完全表达，并在整个成年期（60天及以上）保持稳定。此外，在正常水合的清醒大鼠中，腹腔注射瘦素（0.5 mg/kg）可诱导显著且快速的利尿作用。因此，这些数据构成了大鼠肾脏中[125I]瘦素特异性结合位点的首次表征和定位，并提出了瘦素对肾脏进行调控的可能性。
