Hvor finder glucose reabsorption sted i nyrerne?

Af John Brennan | Opdateret 24. marts 2022

Sådan filtrerer nyrerne blod

Blood enters the kidney through the renal artery, which branches into a network of capillaries that supply the nephrons—the kidney’s functional units. Each adult kidney contains roughly one million nephrons, each composed of a glomerulus and a tubular system where filtration and reabsorption occur.

Glucosefiltrering i glomerulus

Within the glomerulus, high blood pressure forces water, salts, amino acids, and small molecules—including glucose—through the capillary walls into Bowman's capsule. Denne ultrafiltrering fjerner affald og forhindrer samtidig tab af store proteiner og celler.

Glucosereabsorption i den proksimale tubuli

Efter filtrering genvinder den rørformede del af nefronet - specifikt den proksimale tubuli - værdifulde opløste stoffer. Unlike the distal tubule, which secretes waste into the urine, the proximal tubule’s epithelial cells actively transport glucose back into the bloodstream.

Rolle af natrium-afhængige glukose-cotransportører (SGLT2)

På den apikale membran af proksimale tubuliceller sidder SGLT2-proteiner, som kobler natriumreabsorption til glukoseoptagelse. Natriumpumpen opretholder en høj luminal natriumkoncentration; as sodium ions move back into the cell, they drag glucose molecules along, allowing glucose to enter the cell without direct energy expenditure.

Afslut via GLUT2 Transporters

Når først cellen er inde i cellen, kommer glucose ud i blodbanen gennem GLUT2-transportører på den basolaterale membran. GLUT2 operates passively, acting like a revolving door that permits glucose to move from a higher intracellular concentration to the lower plasma level.

In conditions of hyperglycemia, the proximal tubule’s capacity to reabsorb glucose is exceeded, and excess glucose is secreted by the distal tubule and appears in the urine.