Tritto Simona, Gastaldi Giulia, Zelenin Sergey, Grazioli Monica, Orsenigo Maria Novella, Ventura Ulderico, Laforenza Umberto, Zelenina Marina
Department of Experimental Medicine, Section of Human Physiology, University of Pavia, Via Forlanini 6, Pavia, Italy.
Biochem Cell Biol. 2007 Dec;85(6):675-84. doi: 10.1139/o07-142.
Water channels AQP7 and AQP8 may be involved in transcellular water movement in the small intestine. We show that both AQP7 and AQP8 mRNA are expressed in rat small intestine. Immunoblot and immunohistochemistry experiments demonstrate that AQP7 and AQP8 proteins are present in the apical brush border membrane of intestinal epithelial cells. We investigated the effect of several metals and pH on the osmotic water permeability (Pf) of brush border membrane vesicles (BBMVs) and of AQP7 and AQP8 expressed in a cell line. Hg2+, Cu2+, and Zn2+ caused a significant decrease in the BBMV Pf, whereas Ni2+ and Li+ had no effect. AQP8-transfected cells showed a reduction in Pf in the presence of Hg2+ and Cu2+, whereas AQP7-transfected cells were insensitive to all tested metals. The Pf of both BBMVs and cells transfected with AQP7 and AQP8 was not affected by pH changes within the physiological range, and the Pf of BBMVs alone was not affected by phlorizin or amiloride. Our results indicate that AQP7 and AQP8 may play a role in water movement via the apical domain of small intestine epithelial cells. AQP8 may contribute to the water-imbalance-related clinical symptoms apparent after ingestion of high doses of Hg2+ and Cu2+.
水通道蛋白7（AQP7）和水通道蛋白8（AQP8）可能参与小肠的跨细胞水转运。我们发现AQP7和AQP8的mRNA均在大鼠小肠中表达。免疫印迹和免疫组织化学实验表明，AQP7和AQP8蛋白存在于肠上皮细胞的顶端刷状缘膜中。我们研究了几种金属和pH对刷状缘膜囊泡（BBMVs）以及在细胞系中表达的AQP7和AQP8的渗透水通透性（Pf）的影响。Hg2 +、Cu2 +和Zn2 +导致BBMV的Pf显著降低，而Ni2 +和Li +则无影响。在存在Hg2 +和Cu2 +的情况下，转染AQP8的细胞Pf降低，而转染AQP7的细胞对所有测试金属均不敏感。用AQP7和AQP8转染的BBMVs和细胞的Pf不受生理范围内pH变化的影响，单独的BBMV的Pf也不受根皮苷或阿米洛利的影响。我们的结果表明，AQP7和AQP8可能在通过小肠上皮细胞顶端区域的水转运中发挥作用。AQP8可能导致摄入高剂量Hg2 +和Cu2 +后出现的与水失衡相关的临床症状。
