Article Text
Abstract
Background: Preascitic cirrhosis is characterised by subtle renal sodium retention. Calcium inhibits Na+–K+–2Cl− cotransport in the Henle’s loop and could potentially correct sodium-handling abnormalities at that site.
Aim: To investigate the effects of calcium infusion on sodium handling in 10 patients with preascitic cirrhosis and nine healthy controls after 1 week of sodium loading of 200 mmol sodium/day.
Methods: All patients underwent a 3 h supine determination of inulin, para-aminohippurate, lithium and free-water clearances, absolute and fractional excretions of sodium, potassium and calcium and plasma concentrations of renin, aldosterone, norepinephrine and vasopressin. The same were repeated over a further 3 h supine period including 60 min intravenous infusion of 33 mg/min calcium gluconate.
Results: After sodium loading, the 24 h urinary sodium excretion in patients with cirrhosis was lower than that in controls (p<0.03). Calcium infusion significantly decreased plasma norepinephrine levels (p<0.03), and induced greater increases in fractional delivery of sodium to the Henle’s loop (p<0.5) in those with cirrhosis than in controls. This was associated with a decreased fractional reabsorption of sodium beyond the proximal tubule (p<0.03), resulting in greater urinary volume, sodium excretion and free-water clearance in those with cirrhosis than in controls (all with p<0.05). Because the aldosterone-driven potassium secretion, as assessed by the computation of tubular-capillary gradient of [K+] in the collecting duct, was similar in the two groups and unaffected by calcium, sodium retention must have occurred in the Henle’s loop in those with cirrhosis.
Conclusion: Calcium is natriuretic in patients with preascitic cirrhosis; it also decreases norepinephrine release, which could be responsible for decreased reabsorption of sodium in the Henle’s loop.
- AVP, arginine vasopressin
- CIN, inulin steady-state plasma clearance
- CK, potassium clearance
- CNa, sodium clearance
- DFRNa, distal fractional reabsorption of sodium
- FELi, lithium fractional excretion
- GFR, glomerular filtration rate
- IN, inulin
- PAH, para-aminohippurate
- RPF, renal plasma flow
- TAL, thick ascending limb
- TTKR, trans-tubular concentration ratio of potassium in the cortical collecting duct
- UNaV, urinary sodium excretion rate
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- AVP, arginine vasopressin
- CIN, inulin steady-state plasma clearance
- CK, potassium clearance
- CNa, sodium clearance
- DFRNa, distal fractional reabsorption of sodium
- FELi, lithium fractional excretion
- GFR, glomerular filtration rate
- IN, inulin
- PAH, para-aminohippurate
- RPF, renal plasma flow
- TAL, thick ascending limb
- TTKR, trans-tubular concentration ratio of potassium in the cortical collecting duct
- UNaV, urinary sodium excretion rate
Footnotes
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Published Online First 15 February 2007
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*GS’s current address is Gradenigo Hospital, Gastroenterology Unit, Corso Regina Margherita 10, 10153 Torino, Italy; giovannisan{at}iol.it
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Competing interests: None.