How does hypomagnesemia-induced hypokalemia occur?

Updated: Oct 30, 2020
  • Author: Tibor Fulop, MD, PhD, FACP, FASN; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Answer

The mechanism for hypomagnesemia-induced hypokalemia relates to the intrinsic biophysical properties of renal outer medullary K (ROMK) channels mediating K+ secretion in the TAL and the distal nephron. ROMK channels represent the first (Kir1.1) of 7 subfamilies making up the 2-transmembrane segment inward-rectifier potassium channel family. The channels are designated as inward rectifiers because they have a greater inward conductance of potassium ions than they do an outward conductance of them at negative membrane potentials (if external and internal K+ concentrations are equivalent). [35]

The mechanism for this differential conductance results from the binding and subsequent cytoplasmic blocking of the outward K+ movement through the inward-rectifier conduction pathway by cytoplasmic magnesium and polyamines. A reduction in intracellular magnesium (in the absence of polyamines) results in the loss of inward rectification, thus causing the greater outward conductance of K+ ions through the channel pore. Therefore, a decrease in intracellular magnesium concentration in the thick ascending limb of Henle (TAL) and collecting duct cells results in increased K+ secretion through the ROMK channels.

Evidence also suggests that this wasting may be due to a hypomagnesemia-induced decline in adenosine triphosphate (ATP) and the subsequent removal of ATP inhibition of the ROMK channels responsible for secretion in the TAL and collecting duct.


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