Enhanced activity of sodium-lithium countertransport in patients with cardiac syndrome X: a potential link between cardiac and metabolic syndrome X

J Am Coll Cardiol. 1998 Dec;32(7):2031-4. doi: 10.1016/s0735-1097(98)00470-7.


Objectives: This study was aimed at assessing both stimulated insulinemia and the sodium-lithium countertransport in a selected group of patients with cardiac syndrome X.

Background: Hyperinsulinemia, which is frequently present in patients with cardiac syndrome X, is often associated with an enhanced activity of the sodium-lithium countertransport, an in vitro marker of sodium-hydrogen exchange.

Methods: Fifteen patients with syndrome X and 14 matched controls were studied. After pharmacological washout, sodium-lithium countertransport was assessed from lithium-loaded red blood cells. Postload insulin levels were evaluated by a double-antibody radioimmunoassay.

Results: Maximal velocity of sodium-lithium countertransport was higher in patients with syndrome X compared to controls (635+/-200 vs. 324+/-49 micromol/liter/h, p = 0.001). Fourteen of the 15 patients with syndrome X (93%) presented sodium-lithium countertransport values higher than the mean +2 SD of the control group. At 120 min, 12 patients with syndrome X (80%) had plasma levels of insulin >420 pmol/liter, which corresponds to the mean value +2 SD of controls (p = 0.006).

Conclusions: Both enhanced activity of the sodium-lithium countertransport and stimulated hyperinsulinemia are present in the vast majority of patients with cardiac syndrome X. As enhanced activity of the sodium-lithium countertransport has the potential to cause both glucose intolerance and smooth muscle hyperreactivity, it might represent a common cause of the metabolic and vascular alterations frequently found in syndrome X.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biological Transport, Active
  • Erythrocytes / metabolism*
  • Female
  • Humans
  • Insulin / blood
  • Ion Transport
  • Lithium / metabolism*
  • Male
  • Microvascular Angina / blood*
  • Microvascular Angina / physiopathology
  • Middle Aged
  • Radioimmunoassay
  • Sodium / metabolism*


  • Insulin
  • Lithium
  • Sodium