This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
[{'content': 'Used for measuring GFR \nSelect and explain. \nA. Inulin, B. PAH, C. Hippurate, D. D2O', 'role': 'user'}, {'content': 'Answer: A \nExplanation: GLOMERULAR FILTRATION\nGlomerular Membrane (GBM)\nThe barriers through which filtration has to take place\n\nGlomerular endothelial cell layer: (Fenestrated capillary with a gap of 70-90 nm in between endothelium cells)\nBasement membrane: A gel-like acellular meshwork of glycoproteins and proteoglycans.\nVisceral epithelial layer of Bowman’s capsule:\n\ni) The visceral epithelial cell is called a podocyte.\nii) Each podocyte has many foor processes, which interdigitate to form filtration slits.\niii) The slits are approximately 25 nm wide and each is closed by an extremely thin processes called slit diaphragms which bridge the slits between the pedicels.\niv) Slit diaphragms are widened versions of the tight junctions and adhering junctions.\nv) Slit diaphragm is composed of several proteins, including nephrin (NPHS1), NEPH-1, podocin (NPHS2), a-actinin 4 (ACT), and CD2-Ap.\nGlomerular Membrane Permeability Depends on\n\nSize of particle: Neutral substances which are < 4 nm are freely filtered; > 8 nm are not filtered. Between 4 nm and 8 nm, the permeability is inversely proportional to the diameter.\nCharge of the particle: Since the filtration membrane are negatively charged, filtration of positively charged particles is facilitated whereas negatively charged particles are repelled.\nElectron microscopy demonstrates presence of an-ionic sites (negative charge) in all three layers of GBM\n\nMeasuring GFR (mGFR): to detect early damage\n\nClearance of exogenous substances: Inulin, iohexol, 51 CR-EDTA, 125I-iothalamate, 99m Tc-diethylenetriaminepenta-acetic acid (DTPA)\n\n- Evaluation: Precise and accurate, but costly, time-consuming.\n\nClearance of endogenous blood substances\n\n\xa0- Serum creatinine: Insufficiently sensitive for detection of chronic renal disease (CRD)\n- Creatinine clearance: No longer recommended due to errors in urine collection\nException: Patients with highly abnormal muscle mass or vegetarian diet\n- Serum cystatin C: More sensitive than serum creatinine for detection of GFR reduction in the range 70-40; better than creatinine in children.', 'role': 'assistant'}]