Final answer:
The kidneys prevent proteins from being excreted in the urine by filtering blood through glomerular capillaries. Damaged capillaries can cause proteins to leak into the urine, which is an indication of kidney damage such as diabetic nephropathy. Maintaining bodily homeostasis and preventing kidney damage involves managing blood sugar, hypertension, and sodium intake, alongside medical intervention.
Step-by-step explanation:
The kidney is responsible for filtering blood and forming urine. Proteins are large molecules that are not normally filtered out of the blood in the glomeruli. However, if the glomerular capillaries are damaged, proteins like albumin can leak into the filtrate and may end up being excreted in the urine. Such presence of high levels of albumin in urine serves as an indicator of diabetic nephropathy, a disorder of the kidneys.
Proteins do not usually pass through the glomerular capillaries, so only trace amounts should be found in the urine, approximately 10 mg/100 mL. When excessive protein is detected in urine, it suggests that the glomerulus is damaged and is allowing protein to 'leak' into the filtrate. To prevent this, various measures such as controlling high blood sugar, managing hypertension, reducing sodium intake, and using certain drugs can be employed to reduce protein levels and slow kidney damage.
The kidneys also maintain homeostasis by adjusting the reabsorption of necessary substances such as glucose, ions, and amino acids. Carriers such as glucose transport proteins (GLUTs) are involved in transporting these substances, ensuring that any excess is excreted while necessary levels are maintained in the body.