Oppermann Mona, Qin Yan, Lai En Yin, Eisner Christoph, Li Lingli, Huang Yuning, Mizel Diane, Fryc Justyna, Wilcox Christopher S, Briggs Josephine, Schnermann Jurgen, Castrop Hayo
National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, USA.
Am J Physiol Renal Physiol. 2009 Nov;297(5):F1256-64. doi: 10.1152/ajprenal.00264.2009. Epub 2009 Sep 9.
Adenosine 1 receptors (A1AR) in the kidney are expressed in the vasculature and the tubular system. Pharmacological inhibition or global genetic deletion of A1AR causes marked reductions or abolishment of tubuloglomerular feedback (TGF) responses. To assess the function of vascular A1AR in TGF, we generated transgenic mouse lines in which A1AR expression in smooth muscle was augmented by placing A1AR under the control of a 5.38-kb fragment of the rat smooth muscle alpha-actin promoter and first intron (12). Two founder lines with highest expression in the kidney [353 +/- 42 and 575 +/- 43% compared with the wild type (WT)] were used in the experiments. Enhanced expression of A1AR at the expected site in these lines was confirmed by augmented constrictor responses of isolated afferent arterioles to administration of the A1AR agonist N6-cyclohexyladenosine. Maximum TGF responses (0-30 nl/min flow step) were increased from 8.4 +/- 0.9 mmHg in WT (n = 21) to 14.2 +/- 0.7 mmHg in A1AR-transgene (tg) 4 (n = 22; P < 0.0001), and to 12.6 +/- 1.2 mmHg in A1AR-tg7 (n = 12; P < 0.02). Stepwise changes in perfusion flow caused greater numerical TGF responses in A1AR-tg than WT in all flow ranges with differences reaching levels of significance in the intermediate flow ranges of 7.5-10 and 10-15 nl/min. Proximal-distal single-nephron glomerular filtration rate (SNGFR) differences (free-flow micropuncture) were also increased in A1AR-tg, averaging 6.25 +/- 1.5 nl/min compared with 2.6 +/- 0.51 nl/min in WT (P = 0.034). Basal plasma renin concentrations as well as the suppression of renin secretion after volume expansion were similar in A1AR-tg and WT mice, suggesting lack of transgene expression in juxtaglomerular cells. These data indicate that A1AR expression in vascular smooth muscle cells is a critical component for TGF signaling and that changes in renal vascular A1AR expression may determine the magnitude of TGF responses.
肾脏中的腺苷1受体（A1AR）在脉管系统和肾小管系统中表达。对A1AR进行药理学抑制或整体基因敲除会导致显著降低或消除球管反馈（TGF）反应。为了评估血管A1AR在TGF中的功能，我们构建了转基因小鼠品系，通过将A1AR置于大鼠平滑肌α-肌动蛋白启动子和第一个内含子的5.38 kb片段（12）的控制下，增强平滑肌中A1AR的表达。实验中使用了在肾脏中表达最高的两个奠基系[与野生型（WT）相比分别为353±42%和575±43%]。通过分离的传入小动脉对A1AR激动剂N6-环己基腺苷给药的收缩反应增强，证实了这些这些这些品系的预期位点处A1AR表达增强。最大TGF反应（0 - 30 nl/min流量阶跃）从WT中的8.4±0.9 mmHg（n = 21）增加到A1AR转基因（tg）4中的14.2±0.7 mmHg（n = 22；P < 0.0001），以及A1AR - tg7中的12.6±1.2 mmHg（n = 12；P < 0.02）。在所有流量范围内，灌注流量的逐步变化在A1AR - tg中引起的TGF反应数值均大于WT，在7.5 - 10和10 - 15 nl/min的中间流量范围内差异达到显著水平。近端 - 远端单肾单位肾小球滤过率（SNGFR）差异（自由流微穿刺）在A1AR - tg中也增加，平均为6.25±1.5 nl/min，而WT中为2.6±0.51 nl/min（P = 0.034）。A1AR - tg和WT小鼠的基础血浆肾素浓度以及容量扩张后肾素分泌的抑制情况相似，表明在球旁细胞中缺乏转基因表达。这些数据表明血管平滑肌细胞中的A1AR表达是TGF信号传导的关键组成部分，并且肾血管A1AR表达的变化可能决定TGF反应的幅度。
