Question

Why does untreated diabetes cause glucose to be present in collecting duct fluid?

one-two sentence answers, please, that must include the terms: PCT (proximal convoluted tubule) - “reabsorb” or “reabsorption”.

Answer 1

Question: Why does untreated diabetes cause glucose to be present in collecting duct fluid?

Answer: Untreated diabetes causes excessive amount of glucose in circulating blood. In kidneys, blood undergoes the process of glomerular filtration and produces filtrate (tubular fluid) containing water, glucose, electrolytes, and amino acids. Diabetes causes excessive amount of glucose to present in the filtrate. The filtrate that exits the glomerular capillaries pass through the capsular space into the renal tubule . The renal tubule has got three regions: the proximal tubule, nephron loop, and distal tubule. The proximal tubule (PCT) plays a key role in tubular reabsorption. Reabsorption of nearly 100% of nutrients such as glucose and other organic substances back to the blood occurs mainly in the PCT. An increase in the blood glucose level due to diabetes causes excessive amounts of glucose to be present in the filtrate. As the reabsorption of glucose in PCT reaches its limits which is referred to as transport maximum (TM) before all of the glucose is reabsorbed, glucose remains to appear in the filtrate that empties into the collecting system and ultimately in the urine. This condition of the presence of glucose in the urine is referred to as glycosuria, and it is commonly seen with the disorder diabetes mellitus.