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PubMed · 8872960

Cellular mechanisms of the age-related decrease in renal phosphate reabsorption.

V Sorribas·M Lötscher·J Loffing·J Biber·B Kaissling·H Murer·M Levi
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Abstract

The aging process in humans and in the rat is associated with an impairment in renal tubular reabsorption of Pi and renal tubular adaptation to a low Pi diet. The purposes of the present study were to determine whether changes in the abundance of type II Na-Pi contransporter (NaPi-2) protein and/or mRNA play a role in the age-related decrease in Na-Pi cotransport activity, and to further determine the cellular mechanisms of impaired adaptation to a low Pi diet. In studies performed in 3- to 4-month-old young adult rats and 32-to 16-month-old aged rats we found that there was an age-related twofold decrease in proximal tubular apical brush border membrane (BBM) Na-Pi cotransport activity, which was associated with similar decreases in BBM NaPi-2 protein abundance and renal cortical NaPi-2 mRNA level. Immunohisto-chemistry showed lower NaPi-2 protein expression in the BBM of proximal tubules of superficial, midcortical, and juxtamedullary nephrons. We also found that in response to chronic (7 days) and/or acute (4 hr) feeding of a low Pi diet there were similar adaptive increases in BBM Na-Pi cotransport activity and BBM NaPi-2 protein abundance in both young and aged rats. However, BBM Na-Pi cotransport activity and BBM NaPi-2 protein abundance were still significantly lower in aged rats, in spite of a significantly lower serum Pi concentration in aged rats. The results indicate that impaired expression of the type II renal Na-Pi cotransporter protein at the level of the apical BBM plays an important role in the age-related impairment in renal tubular reabsorption of Pi and renal tubular adaptation to a low Pi diet.

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Adaptation, PhysiologicalAgingAnimalsBlotting, NorthernCarrier ProteinsImmunohistochemistryKidneyKidney Tubules, ProximalMalePhosphatesPhosphorus, DietaryRNA, MessengerRatsRats, Sprague-DawleySodium-Phosphate Cotransporter ProteinsSodium-Phosphate Cotransporter Proteins, Type IISymportersJournal ArticleResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.

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V Sorribas, M Lötscher, J Loffing, J Biber, B Kaissling, H Murer, M Levi. 1996. Cellular mechanisms of the age-related decrease in renal phosphate reabsorption.. https://doi.org/10.1038/ki.1996.385

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