ROMK

• OMIM: 600359

• MGI: 1927248

ROMK is the abbreviation for " Renal Outer Medullary Potassium (K ) channel" ( engl., =, potassium channel of the outer medulla '), an ion channel, which exerts an important role in the excretion of potassium in the kidney. ROMK encoded by the gene KIR1.1. Mutations in this gene lead to congenital disorders of potassium homeostasis.

Expression of ROMK in the kidney

In Nephron, the functional sub- unit of the kidney, ROMK is expressed in two different sections, and performs different functions therein.

In the thick ascending limb ( leg ) of the loop of Henle are first transported via the Na-K- 2Cl cotransporter from the primary through the lumen-side ( apical ) cell membrane into the tubule sodium and potassium. While sodium and chloride is transported from the tubular cell of the lumen distant ( basolateral ) membrane into the blood ( reabsorption ) potassium on ROMK passes back into the apical membrane in the primary urine, and is there again for the transport of sodium and chloride in the cell. ROMK is responsible to some extent for the recycling of potassium in the loop of Henle. This recycling favors the one hand the reabsorption of sodium chloride from the primary urine into the blood. On the other hand, the potassium recycling via ROMK to increase the positive charge in the primary urine, and this, in turn, facilitates the transport of calcium and magnesium from the primary into the blood.

In the manifold ROMK is also expressed in the apical membrane of the cell collection tube, but there is responsible for the secretion of potassium from the blood into the urine. In the collecting duct, the largest share of the excess over the food supplied potassium is excreted in the urine via ROMK. If the potassium dietary intake to the density of ROMK increases in the collecting duct of the kidney. This is interpreted as an adaptation to the lifestyle of our ancestors in the Paleolithic, who have taken a diet rich in potassium and low in salt to himself.

Medical importance

The loss of function of ROMK by a mutation leads to Bartter syndrome type II Immediately after birth, the affected children to a high potassium levels in the blood ( hyperkalemia ), this is attributed to the decreased excretion of potassium in the collecting duct of the kidney. In the further course of the disease the potassium level in the blood drops, it comes to hypokalemia. This is explained by the fact that in the loop of Henle the recycling of potassium fails on ROMK, thereby inhibiting the reabsorption of sodium chloride, calcium and magnesium from the primary urine into the blood. The sodium concentration in the primary urine increases, the collection tube, the urine flow increases. This means that in the collecting pipe, a second cell potassium channel Maxi potassium channel is activated, which is closed during normal flow and normal saline concentration. This ultimately leads to a loss of potassium through the kidneys and a decrease in potassium concentration in the blood. The time course of the disease with elevated potassium levels immediately after birth and decrease of potassium in the further course of the disease is characterized explains that sooner expressed in the development of kidney ROMK as Maxi -K . Result of the disease are severe salt and potassium loss through the kidneys, until the dissolution of muscle cells (rhabdomyolysis), and periodic paralysis (Periodic paralysis ) can perform as well as growth disorders and mental development.