Document Detail


Mitochondrial aquaporin-8 in renal proximal tubule cells: Evidence for a role in the response to metabolic acidosis.
MedLine Citation:
PMID:  22622463     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Mitochondrial ammonia synthesis in proximal tubules and its urinary excretion are key components of the renal response to maintain acid-base balance during metabolic acidosis. Since aquaporin-8 (AQP8) facilitates transport of ammonia and is localized in inner mitochondrial membrane (IMM) of renal proximal cells, we hypothesized that AQP8-facilitated mitochondrial ammonia transport in these cells plays a role in the response to acidosis. We evaluated whether mitochondrial AQP8 (mtAQP8) knockdown by RNA interference is able to impair ammonia excretion in the human renal proximal tubule cell line, HK-2. By RT-PCR and immunoblotting we found that AQP8 is expressed in these cells and is localized in IMM. HK-2 cells were transfected with siRNA targeting human AQP8. After 48 h, the levels of mtAQP8 protein decreased by 53 % (P < 0.05). mtAQP8 knockdown decreased the rate of ammonia released into culture medium in cells grown at pH 7.4 (-31 % P < 0.05) as well as in cells exposed to acid (-90 % P < 0.05). We also evaluated mtAQP8 protein expression in HK-2 cells exposed to acidic medium. After 48 h, upregulation of mtAQP8 (+74 % P < 0.05) was observed, together with higher ammonia excretion rate (+73 % P < 0.05). In vivo studies in NH4Cl-loaded rats showed that mtAQP8 protein expression was also upregulated after 7 days of acidosis in renal cortex (+51 % P < 0.05). These data suggest that mtAQP8 plays an important role in the adaptive response of proximal tubule to acidosis possibly facilitating mitochondrial ammonia transport.
Authors:
Sara Maria Molinas; Laura Trumper; Raúl Alberto Marinelli
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-5-23
Journal Detail:
Title:  American journal of physiology. Renal physiology     Volume:  -     ISSN:  1522-1466     ISO Abbreviation:  -     Publication Date:  2012 May 
Date Detail:
Created Date:  2012-5-24     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  100901990     Medline TA:  Am J Physiol Renal Physiol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
1Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET.
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