title: Determination of postglomerular permselectivity to neutral dextrans in the dog.
abstract: The single-pass multiple-indicator-dilution (MID) technique was used to analyze postglomerular capillary permeability. Anesthetized mongrel dogs (n = 13) during mannitol diuresis received a pulse injection of 125I-albumin (plasma reference), [14C]inulin (glomerular reference), creatinine (interstitial reference), and a homogeneous [3H]dextran molecular weight marker 6,000-12,000 dalton in the left renal artery. Simultaneous left renal venous outflow and right and left urine were rapidly sampled. Left urine recoveries of creatinine, [14C]inulin, and [3H]dextran were identical, indicating no glomerular solute flux limitation. Progressive precession of the [14C]inulin and [3H]dextran renal vein curves relative to creatinine indicated increasing postglomerular limitation to solute flux proportional to molecular size. The postglomerular solute extraction (EPG) (renal vein upslope indicator/125I-albumin) varied inversely with postglomerular renal plasma flow (F), indicating diffusion limitation. Ouabain infusion into the left renal artery significantly reduced Na reabsorption but did not alter the EPG of [14C]inulin or [3H]dextran. Permeability-surface (PS) area products calculated from EPG and F ranged from 4.86 +/- 0.89 to 0.97 +/- 0.25 (SD) cm X s-1 X 100 g-1 for indicators 5,000-12,000 dalton. [14C]Inulin PS products remained constant for F greater than or equal to 2.50 ml X s-1 X 100 g kidney-1. PS[3H]dextran/PS[14C]In (n = 20, F greater than or equal to 2.5 ml X s-1) was used to calculate an effective postglomerular capillary pore radius, r = 55.5 +/- 7.6 (SD) A.
mesh_terms: D000818:Animals; D002196:Capillaries / Q000502:physiology; D002250:Carbon Radioisotopes; D003911:Dextrans / Q000378:metabolism*; D004285:Dogs; D005260:Female; D007444:Inulin / Q000378:metabolism; D007457:Iodine Radioisotopes; D007678:Kidney Glomerulus / Q000502:physiology*; D007700:Kinetics; D008297:Male; D008970:Molecular Weight; D010539:Permeability; D012079:Renal Circulation; D012709:Serum Albumin / Q000378:metabolism; D013329:Structure-Activity Relationship; D014316:Tritium
chemical_list: D002250:Carbon Radioisotopes; D003911:Dextrans; D007457:Iodine Radioisotopes; D012709:Serum Albumin; D014316:Tritium; D007444:Inulin