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Natriuretic and aquaretic effects of intravenously infused calcium in preascitic human cirrhosis: physiopathological and clinical implications
  1. G Sansoè,
  2. F Wong
  1. Division of Gastroenterology, Department of Medicine, Toronto General Hospital, University of Toronto, Toronto, Ontario, Canada
  1. Correspondence to:
    Dr F Wong
    Division of Gastroenterology, Department of Medicine, 9N/983 Toronto General Hospital, 200 Elizabeth Street, Toronto, Ontario, Canada M5G 2C4;florence.wong{at}utoronto.ca

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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Footnotes

  • Published Online First 15 February 2007

  • *GS’s current address is Gradenigo Hospital, Gastroenterology Unit, Corso Regina Margherita 10, 10153 Torino, Italy; giovannisan{at}iol.it

  • Competing interests: None.

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