16. Glucose clearance Flashcards
Glucose clearance - describe
glucose at a normal plasma level is completely reabsorbed in proximal concoluted tubule bby Na+/ glucose contrasport
glucose in serum ( normally)
fasting : 70 -110 mg / dL (3.8-6.1 mmmol/L )
2h postprandial : less τηαν 120 mg/dL , less than 6.6 mmol /L
glucose in cerebrospinal fluid
40-70 mg/dL
2.2-3.9 mmol/L
glucose in urine - concrentations ( adults
In adults, at plasmaglucose of 200 mg / dL –> glucosouria begins . At rate 375 mg/ min , all transporters are fully saturated
glucosuria is an importan t clinical clue to
diabetes mellitus
glucose clearance - splay ?
is the region of substance clearance between threshold and Tm –> it is due to heterogeneity of nephrons
glucose clearance - pregnancy
normal pregnancy may decreae ability of proximal conluted tubule to reabsorb glucose and aminoacids –> glucosouria and aminoaciduria
mechanism that induce glucosouria and aminoaciduria in normal pregnancy
normal pregnancy may decrease ability of proximal convoluted tubule to reabsorb glucose and aminoacids
• In the nephron, glucose is ___ (partially/fully) reabsorbed in ___ the (proximal/distal) tubules via Na+/glucose cotransporters.
Fully; proximal
• When plasma glucose levels exceed 200 mg/dL, what finding may result on urinalysis? What disease process is usually suspected?
Glucosuria, because proximal tubule glucose reabsorption mechanisms cannot keep up with the elevated glucose load; diabetes mellitus
• A diabetic’s blood sugar is 275 mg/dL; the urine is positive for glucose. Can proximal tubule pumps handle further blood-sugar increases?
Yes—the glucose threshold of 200 mg/dL has been passed, but the transporters are not fully saturated (Tm) until the level passes 375 mg/dL
• Glucosuria and aminoaciduria develop in a pregnant woman. Do you immediately diagnose diabetes?
No—normal pregnancy decreases reabsorption of glucose and amino acids in the proximal tubule, resulting in glucosuria and aminoaciduria
