Two models of glomerular filtration rate and renal blood flow in the rat |
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Authors: | Ronald E Huss Donald J Marsh Robert E Kalaba |
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Institution: | (1) Department of Biomedical Engineering, Graduate Center for Engineering Studies, University of Southern California, 90007 Los Angeles, California |
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Abstract: | Two mathematical models of glomerular filtration and blood flow are derived. The first is based on principles of fluid and
mass conservation in individual capillaries. The model explains why the filtration rate (GFR) is strongly dependent on local
hydrostatic and protein oncotic pressures, and on plasma flow rate (GCPF), but only weakly dependent on exact numbers, lengths,
radii, or filtration coefficient of glomerular capillaries. The model shows that much of the increased GFR in both isooncotic
plasma loading and isotonic Ringer's loading is due to increased GCPF caused by diluting erythrocytes. The second model uses
several approximations and reduces to a quadratic in afferent arteriolar blood flow. When arterial pressure, hematocrit, plasma
protein concentration, and afferent and efferent arteriolar resistances are specified, the model predicts GFR, afferent arteriolar
blood flow, and filtration fraction. Alternatively, if any two of these three variables are known, the model predicts segmental
arteriolar resistances. The model indicates that GFR and blood flow regulation must be located in the afferent arteriole,
despite the strong dependence of GFR on GCPF. |
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Keywords: | |
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