title: The water channel aquaporin-1 contributes to renin cell recruitment during chronic stimulation of renin production.
abstract: Both the processing and release of secretory granules involve water movement across granule membranes. It was hypothesized that the water channel aquaporin (AQP)1 directly contributes to the recruitment of renin-positive cells in the afferent arteriole. AQP1(-/-) and AQP1(+/+) mice were fed a low-salt (LS) diet [0.004% (wt/wt) NaCl] for 7 days and given enalapril [angiotensin-converting enzyme inhibitor (ACEI), 0.1 mg/ml] in drinking water for 3 days. There were no differences in plasma renin concentration at baseline. After LS-ACEI, plasma renin concentrations increased markedly in both genotypes but was significantly lower in AQP1(-/-) mice compared with AQP1(+/+) mice. Tissue renin concentrations were higher in AQP1(-/-) mice, and renin mRNA levels were not different between genotypes. Mean arterial blood pressure was not different at baseline and during LS diet but decreased significantly in both genotypes after the addition of ACEI; the response was faster in AQP1(-/-) mice but then stabilized at a similar level. Renin release after 200 μl blood withdrawal was not different. Isoprenaline-stimulated renin release from isolated perfused kidneys did not differ between genotypes. Cortical tissue norepinephrine concentrations were lower after LS-ACEI compared with baseline with no difference between genotypes. Plasma nitrite/nitrate concentrations were unaffected by genotype and LS-ACEI. In AQP1(-/-) mice, the number of afferent arterioles with recruitment was significantly lower compared with AQP1(+/+) mice after LS-ACEI. We conclude that AQP1 is not necessary for acutely stimulated renin secretion in vivo and from isolated perfused kidneys, whereas recruitment of renin-positive cells in response to chronic stimulation is attenuated or delayed in AQP1(-/-) mice.
authors.affiliation: Department of Cardiovascular and Renal Research, University of Southern Denmark, Odense, Denmark;
authors.forename: Anne R
authors.initials: AR
authors.lastname: Tinning
authors.affiliation: Department of Cardiovascular and Renal Research, University of Southern Denmark, Odense, Denmark; bljensen@health.sdu.dk.
authors.forename: Boye L
authors.initials: BL
authors.lastname: Jensen
authors.affiliation: Institute of Physiology, University of Regensburg, Regensburg, Germany;
authors.forename: Frank
authors.initials: F
authors.lastname: Schweda
authors.affiliation: Institute of Physiology, University of Regensburg, Regensburg, Germany;
authors.forename: Katharina
authors.initials: K
authors.lastname: Machura
authors.affiliation: Department of Cardiovascular and Renal Research, University of Southern Denmark, Odense, Denmark;
authors.forename: Pernille B L
authors.initials: PB
authors.lastname: Hansen
authors.affiliation: Department of Cardiovascular and Renal Research, University of Southern Denmark, Odense, Denmark;
authors.forename: Jane
authors.initials: J
authors.lastname: Stubbe
authors.affiliation: Department of Neurobiology Research, University of Southern Denmark, Odense, Denmark; and.
authors.forename: Jan Bert
authors.initials: JB
authors.lastname: Gramsbergen
authors.affiliation: Department of Cardiovascular and Renal Research, University of Southern Denmark, Odense, Denmark; Department of Pathology, Odense University Hospital, Odense, Denmark.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Madsen
mesh_terms: D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology; D000818:Animals; D051398:Aquaporin 1 / Q000235:genetics / Q000378:metabolism*; D001794:Blood Pressure / Q000235:genetics / Q000502:physiology; D003594:Cytoplasmic Granules / Q000187:drug effects / Q000378:metabolism; D004039:Diet, Sodium-Restricted; D005260:Female; D066298:In Vitro Techniques; D007668:Kidney / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009566:Nitrates / Q000378:metabolism; D009638:Norepinephrine / Q000378:metabolism; D011247:Pregnancy; D012079:Renal Circulation / Q000187:drug effects; D012083:Renin / Q000096:biosynthesis* / Q000378:metabolism*
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D009566:Nitrates; D051398:Aquaporin 1; D012083:Renin; D009638:Norepinephrine
keywords: blood pressure; exocytosis; nitric oxide; norepinephrine; secretion