Rhoten W B, Bruns M E, Christakos S
Endocrinology. 1985 Aug;117(2):674-83. doi: 10.1210/endo-117-2-674.
We looked for the presence of vitamin D-dependent intestinal calcium binding protein (CaBP), relative molecular mass (mol wt) about 10,000, in kidneys of mammals, birds, and reptiles, and compared the localization of this 10,000 mol wt CaBP with the localization of the 28,000 mol wt vitamin D-dependent CaBP. Antiserum directed against rat intestinal CaBP (RICaBP) was used with the unlabeled antibody peroxidase-antiperoxidase technique to localize the 10,000 mol wt CaBP. Kidneys of adult Swiss and DBA/2J mice were positive for the 10,000 mol wt CaBP, whereas kidneys of adult rat, chicken, and two species of lizard were negative. Extracts of adult rat kidney showed no detectable immunoreactivity with the antiserum to RICaBP by radial immunodiffusion assay. However, kidneys of postnatal rats (12 days old) exhibited limited immunocytochemical reactivity and relatively low immunoreactivity (about 1 micrograms/mg protein) for 10,000 mol wt CaBP. In both strains of mice, 10,000 mol wt CaBP was localized predominantly to the distal convoluted tubules, connecting tubules, and collecting tubules of the cortical labyrinth. In 12-day-old rats 10,000 mol wt CaBP was localized to the distal convoluted tubules and cortical ascending thick limbs. Absorption of the antiserum with electrophoretically pure RICaBP eliminated specific reactivity. By dual color staining of mouse kidneys, the population of cells reactive for the 10,000 mol wt CaBP was found to be similar, but not identical, to that population of cells reactive for the 28,000 mol wt CaBP. Absorption of the antiserum to RICaBP with either rat renal CaBP or chicken intestinal CaBP (both 28,000 mol wt CaBPs) had no affect on the positive reactivity of the distal mouse nephron for RICaBP. Conversely, absorption of the antiserum to rat renal CaBP with the 10,000 mol wt RICaBP had no affect on reactivity for the 28,000 mol wt CaBP. Thus, two immunologically distinct CaBPs, mol wt 10,000 and 28,000, are present in the adult mouse nephron; whereas, kidneys of adult rats, chickens, and saurian reptiles apparently contain significant levels of only 28,000 mol wt CaBP. Since the 12-day-old rat nephron contains both the 28,000 mol wt and the 10,000 mol wt CaBP it appears that in the kidney, ontogenetically, and perhaps evolutionarily as well, the 28,000 mol wt CaBP is more highly conserved.
我们探寻了维生素D依赖性肠钙结合蛋白（CaBP）（相对分子质量约为10,000）在哺乳动物、鸟类和爬行动物肾脏中的存在情况，并将这种10,000相对分子质量的CaBP的定位与28,000相对分子质量的维生素D依赖性CaBP的定位进行了比较。用针对大鼠肠CaBP（RICaBP）的抗血清，采用未标记抗体过氧化物酶-抗过氧化物酶技术来定位10,000相对分子质量的CaBP。成年瑞士小鼠和DBA/2J小鼠的肾脏对10,000相对分子质量的CaBP呈阳性反应，而成年大鼠、鸡和两种蜥蜴的肾脏呈阴性反应。成年大鼠肾脏提取物通过放射免疫扩散测定法显示，与针对RICaBP的抗血清无明显免疫反应性。然而，出生后12天的大鼠肾脏对10,000相对分子质量的CaBP表现出有限的免疫细胞化学反应性和相对较低的免疫反应性（约1微克/毫克蛋白质）。在这两种品系的小鼠中，10,000相对分子质量的CaBP主要定位于皮质迷路的远曲小管、连接小管和集合小管。在12天大的大鼠中，10,000相对分子质量的CaBP定位于远曲小管和皮质升支粗段。用经电泳纯化的RICaBP吸收抗血清可消除特异性反应性。通过对小鼠肾脏进行双色染色发现，对10,000相对分子质量的CaBP有反应的细胞群体与对28,000相对分子质量的CaBP有反应的细胞群体相似，但不完全相同。用大鼠肾CaBP或鸡肠CaBP（均为28,000相对分子质量的CaBPs）吸收针对RICaBP的抗血清，对小鼠远端肾单位对RICaBP的阳性反应性没有影响。相反，用10,000相对分子质量的RICaBP吸收针对大鼠肾CaBP的抗血清，对28,000相对分子质量的CaBP的反应性没有影响。因此，成年小鼠肾单位中存在两种免疫上不同的CaBPs，相对分子质量分别为10,000和28,000；而成年大鼠、鸡和蜥蜴类爬行动物的肾脏显然仅含有大量的28,000相对分子质量的CaBP。由于12天大的大鼠肾单位同时含有28,000相对分子质量和10,000相对分子质量的CaBP，似乎在肾脏中，从个体发生角度，也许在进化角度也是如此，28,000相对分子质量的CaBP更具保守性。
