Final answer:
Glomerular Filtration Rate (GFR) is the volume of glomerular filtrate formed per minute by the kidneys and is an important indicator of kidney function. Solute conditions for GFR estimates require the solute to be neither reabsorbed nor secreted by the kidney. Factors that can increase or decrease GFR include blood pressure, arteriole dilation or constriction, and certain drugs.
Step-by-step explanation:
Glomerular Filtration Rate (GFR) and Solute Conditions
The GFR is the volume of glomerular filtrate formed per minute by the kidneys. It is regulated by multiple mechanisms and is an important indicator of kidney function. GFR can be estimated by measuring naturally occurring creatinine, a protein-derived molecule produced by muscle metabolism that is not reabsorbed and only slightly secreted by the nephron. In order for a solute to be used for GFR estimates, it should ideally be neither reabsorbed nor secreted by the kidney.
Factors Affecting GFR
- Increase GFR: High blood pressure, dilation of the afferent arteriole, low levels of angiotensin II, increased plasma osmolarity, and certain drugs like diuretics.
- Decrease GFR: Low blood pressure, constriction of the afferent arteriole, high levels of angiotensin II, decreased plasma osmolarity, and certain drugs like ACE inhibitors.
Importance of Reabsorption
Around 99% of the filtrate is normally reabsorbed in the renal tubules. Reabsorption is important because it allows the body to retain necessary substances like glucose, amino acids, and ions, while selectively removing waste products like urea and toxins. Without reabsorption, valuable substances would be lost in the urine and waste products would accumulate in the body.