Abstract

Background: Exposure to microgravity results in alterations of renal function, fluid redistribution and bone loss which contributes to the potential risk of renal stone formation. Hypercalciuria is recognized as a condition predisposing to calcium nephrolitiasis and long-term space flights cause bone loss coupled to a rise of urinary calcium excretion. Methods: AQP2 excretion was measured by ELISA in urines collected from healthy volunteers participating at the studies. Results: We recently demonstrated that high calcium delivery to the collecting duct reduces local Aquaporin 2 (AQP2) mediated water reabsorption under vasopressin action, thus limiting the maximal urinary concentration and reducing calcium saturation. To analyze alteration of renal water handling during microgravity, we evaluated two ground-based analog of spaceflight, thermoneutral water immersion and bed rest. AQP2 excretion and diuresis were measured in two separated studies mimicking acute adaptation (6 hours water immersion) or chronic adaptation (35 days bed rest) to microgravity. Water immersion resulted in a significant increase in urinary output apparently not related to AQP2 alteration and manly due to reduced vasopressin secretion. On the other hand 35 days bed rest resulted in an increase in urinary calcium, which coincided with a significant decrease in AQP2 excretion (645±7.4 fmol/ml to 569±10.3 fmol/ml), which is expected to result in urine dilution reducing the risk of calcium saturation. Conclusions: Our data indicate that calciuria and water balance have to be strictly controlled during microgravity and long-term bed rest as key elements for the risk of kidney stone formation.

Autore Pugliese

• Valenti Giovanna

Tutti gli autori

• VALENTI G.;SVELTO M.;RANIERI M.

Titolo volume/Rivista

Non Disponibile

Anno di pubblicazione

2013

ISSN

1046-6673

ISBN

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Numero di citazioni Wos

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Settori ERC

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