Why do loop diuretics reduce Ca/Mg reabsorption?

[studylol]

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Control of Mg and Ca reabsorption is controlled by how positive the filtrate in the nephron is. If its more +, then Mg/Ca have a stronger tendency to be reabsorbed.

So if we have loop diuretics, then at the thick ascending limb of the loop of henle, NKCC2 are blocked. How does this translate into attenuation of Mg/Ca reabsorption?

thanks!

 

[deleted564496]

My understanding is that the Na-K-Cl pump drives the paracellular reabsorption of Calcium + Magnesium... I'm not sure if this is correct, but my impression is that the paracellular gradient is created by potassium going back out into the filtrate by the ROMK channels.. Thus, in exchange the Calcium + Magnesium can be reabsorbed... Again I'm not sure if this is correct, but just what made sense to me.

 

[Transposony]

Normally, there is active reabsorption of Na+, K+, and Cl- by Na+/K+/2Cl– cotransporter at the thick ascending loop of Henle which indirectly induces the paracellular reabsorption of Mg2+ and Ca2+ through (+) lumen potential generated by K+ backleak.
Loop diuretics inhibits Na+/K+/2Cl– cotransporter at the thick ascending loop of Henle. So, no K+ backleak, no paracellular reabsorption of Mg2+ and Ca2+.

 

[EazyE1907]

Normally, there is active reabsorption of Na+, K+, and Cl- by Na+/K+/2Cl– cotransporter at the thick ascending loop of Henle which indirectly induces the paracellular reabsorption of Mg2+ and Ca2+ through (+) lumen potential generated by K+ backleak.
Loop diuretics inhibits Na+/K+/2Cl– cotransporter at the thick ascending loop of Henle. So, no K+ backleak, no paracellular reabsorption of Mg2+ and Ca2+.

yup simple as that. no reabs of na,k, and cl-, no back leak, no mg and ca reabs

 

[studylol]

Thanks very much!

 

[worldbeater]

The triple transport (Na-K-2cl) is correct as described above, and loop diuretics do block this system, but be careful with the normal functioning of Mg and Ca. The sodium co-transporter can only move ONE ion at a time, either Mg or Ca, they both use the same co-transporter.

So this is called the "yo-yo" effect, when the transporter tries to correct one deficiency after another. If you have hypocalcemia, you reabsorb calcium to bring the value to baseline, but you end up not being able to reabsorb Mg, and your value of Mg drops. When you try to correct Mg, the value of Ca drops.

The way to correct both the hypocalcemia and hypomagnesemia is to administer two drugs that contain each ion, calcium gluconate and magnesium sulphate.