Angiotensin II and hypertonicity modulate proximal tubular aquaporin 1 expression
| Autor: | Flavia F. Jung, Hua A. Lu, Ivan Sabolić, Julie R. Ingelfinger, Dennis Brown, Hiroyuki Kobori, Richard Bouley, Shiow-Shih Tang, Winnie W. C. Shum, Zaira Palomino, Paula Nunes |
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| Rok vydání: | 2009 |
| Předmět: |
renin angiotensin system
proximal tubule Male medicine.medical_specialty Time Factors Physiology Hypertonic Solutions Tetrazoles Sodium Chloride Kidney Losartan Kidney Tubules Proximal Rats Sprague-Dawley Internal medicine Renin–angiotensin system medicine Loop of Henle Animals RNA Messenger Cell Line Transformed Angiotensin II receptor type 1 Aquaporin 1 Dose-Response Relationship Drug Chemistry Reabsorption Angiotensin II Imidazoles Drug Synergism Articles Diuresis Rats medicine.anatomical_structure Endocrinology cardiovascular system Angiotensin II Type 1 Receptor Blockers hormones hormone substitutes and hormone antagonists medicine.drug |
| Zdroj: | American Journal of Physiology-Renal Physiology. 297:F1575-F1586 |
| ISSN: | 1522-1466 1931-857X |
| Popis: | Aquaporin 1 (AQP1) is the major water channel in the renal proximal tubule (PT) and thin descending limb of Henle, but its regulation remains elusive. Here, we investigated the effect of ANG II, a key mediator of body water homeostasis, on AQP1 expression in immortalized rat proximal tubule cells (IRPTC) and rat kidney. Real-time PCR on IRPTC exposed to ANG II for 12 h revealed a biphasic effect AQP1 mRNA increased dose dependently in response to 10−12 to 10−8 M ANG II but decreased by 50% with 10−7 M ANG II. The twofold increase of AQP1 mRNA in the presence of 10−8 M ANG II was abolished by the AT1 receptor blocker losartan. Hypertonicity due to either NaCl or mannitol also upregulated AQP1 mRNA by three- and twofold, respectively. Immunocytochemistry and Western blotting revealed a two- to threefold increase in AQP1 protein expression in IRPTC exposed concomitantly to ANG II (10−8M) and hypertonic medium (either NaCl or mannitol), indicating that these stimuli were not additive. Three-dimensional reconstruction of confocal images suggested that AQP1 expression was increased by ANG II in both the apical and basolateral poles of IRPTC. In vivo studies showed that short-term ANG II infusion had a diuretic effect, while this effect was attenuated after several days of ANG II infusion. After 10 days, we observed a twofold increase in AQP1 expression in the PT and thin descending limb of Henle of ANG II-infused rats that was abolished when rats were treated with the selective AT1-receptor antagonist olmesartan. Thus ANG II increases AQP1 expression in vitro and in vivo via direct interaction with the AT1 receptor, providing an important regulatory mechanism to link PT water reabsorption to body fluid homeostasis via the renin-angiotensin system. |
| Databáze: | OpenAIRE |
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