Ozono R, Wang Z Q, Moore A F, Inagami T, Siragy H M, Carey R M
Department of Medicine, University of Virginia Health Sciences Center, Charlottesville 22908, USA.
Hypertension. 1997 Nov;30(5):1238-46. doi: 10.1161/01.hyp.30.5.1238.
In situ hybridization studies have suggested that the subtype 2 angiotensin (AT2) receptor gene is expressed in fetal and newborn rat kidney but is undetectable in the adult animals. In the present study, we investigated the expression of AT2 receptor protein in the fetal (days 14 and 19 of fetal life), newborn (day 1 postpartum), and adult (4-week-old and 3-month-old) rat kidney. Polyclonal anti-peptide antiserum was raised against the amino terminus of the native AT2 receptor. The selectivity of the antiserum was validated by recognition of the AT2 receptor in a stably transfected COS-7 cell line by Western blot and immunocytochemical analysis. As a positive control, the AT2 receptor signal was detected strongly in the adrenal gland. Positive immunohistochemical staining was observed in the mesenchymal cells and ureteric buds of the 14-day fetal kidney and in the glomeruli, tubules, and vessels in the 19-day fetal and newborn kidney. Glomeruli expressing the AT2 receptor were localized mainly in the outer layer of the renal cortex. In the young (4-week-old) and mature (3-month-old) adult rat on normal sodium intake, renal AT2 receptor immunoreactivity was present in glomeruli but substantially diminished compared with that of newborn rats. In both young and mature adult rats, dietary sodium depletion increased the renal AT2 receptor signal, mainly in the glomeruli and interstitial cells. Preimmune and preadsorption controls were negative. Western blot analysis detected a single 44-kD band in the fetal and newborn rat kidney and in the young and mature adult rat kidney. Dietary sodium depletion increased the density of the AT2 receptor band in mature adult rat kidneys. These data provide evidence that the AT2 receptor protein is expressed in the fetal and newborn rat kidney, diminishes in adult life, and is reexpressed in the adult in response to sodium depletion.
原位杂交研究表明，2型血管紧张素（AT2）受体基因在胎鼠和新生大鼠肾脏中表达，但在成年动物中无法检测到。在本研究中，我们调查了AT2受体蛋白在胎鼠（胎龄14天和19天）、新生鼠（出生后1天）以及成年大鼠（4周龄和3月龄）肾脏中的表达情况。针对天然AT2受体的氨基末端制备了多克隆抗肽抗血清。通过蛋白质印迹法和免疫细胞化学分析，在稳定转染的COS-7细胞系中识别AT2受体，验证了抗血清的选择性。作为阳性对照，在肾上腺中强烈检测到AT2受体信号。在14天胎龄的肾脏间充质细胞和输尿管芽以及19天胎龄和新生鼠肾脏的肾小球、肾小管和血管中观察到阳性免疫组化染色。表达AT2受体的肾小球主要位于肾皮质外层。在正常钠摄入的幼年（4周龄）和成年（3月龄）大鼠中，肾小球中存在肾脏AT2受体免疫反应性，但与新生大鼠相比显著降低。在幼年和成年大鼠中，饮食中钠缺乏均增加了肾脏AT2受体信号，主要在肾小球和间质细胞中。免疫前和吸附前对照均为阴性。蛋白质印迹分析在胎鼠和新生大鼠肾脏以及幼年和成年大鼠肾脏中检测到一条单一的44-kD条带。饮食中钠缺乏增加了成年大鼠成熟肾脏中AT2受体条带的密度。这些数据提供了证据，表明AT2受体蛋白在胎鼠和新生大鼠肾脏中表达，在成年期减少，并在成年期因钠缺乏而重新表达。
