Regulation of Glomerular Filtration Rate - Renal Clearance 2 Flashcards
What is the importance of inulin in assessing renal function?
- Is a glomerular marker: clearance = GFR
- Is a reference substance: Clearance ratio of a substance X
= Cx/Cinulin
Reasons the Cx = Cin
◦ Filtration
◦ No reabsorption & secretion
Reasons that Cx could be less than Cin?
◦ Filtration + Reabsorption
◦ No filtration (i.e., albumin)
Reasons Cx could be higher than Cin?
◦ Filtration + Secretion
Why is creatinine?
endogenous product of muscle metabolism
Describe the rate of production of creatinine.
fairly constant
What organ is creatinine mostly cleared from the body by?
kidneys
Renal handling of Creatinine.
◦ Free filtration
◦ Lack of reabsorption ◦ Small secretion
How will low GFR affect plasma creatinine?
increase plasma creatinine levels
Does plasma concentration of creatinine depend on GFR or production rate?
GFR
doesn’t depend on production rate because it relatively constant
Normal blood level for creatinine.
Adule males 0.8 -1.3 mg/dL
Adult female: 0.6 - 1.0 mg/dL
Describe the renal handling of urea.
◦ Free filtration
◦ Reabsorbed in variable amounts
(~50%)
◦ Lack of secretion
Plasma concentration of urea increases when GFR increases or decreases?
When GFR decreases
Describe rate of production of urea.
Considerable variations in the rate of production (protein intake, catabolic rate)
Free water clearance in Iso-osmotic urine.
◦ Free water clearance (CH20)= 0
Be able to reproduce this chart on substances that assess renal clearance.
Be able to answer the questions.
