Laboratory Investigation

Kidney International (1982) 21, 309–315; doi:10.1038/ki.1982.23

Internephron heterogeneity of filtration fraction and disparity between protein- and hematocrit-derived values

Bruce Jackson1 and Donald E Oken1

1Department of Medicine, Medical College of Virginia, and the McGuire Veterans Administration Hospital, Richmond, Virginia

Correspondence: Dr D E Oken, Box 160, Medical College of Virginia, Richmond, Virginia 23298, USA

Received 28 April 1981; Revised 17 July 1981.

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Abstract

Internephron heterogeneity of filtration fraction and disparity between protein and hematocrit-derived values. The variability of single nephron filtration fraction (SNFF) and the relationship between filtration fractions determined simultaneously from 125I albumin (SNFFALB) and hematocrit (SNFFHCT) values were assessed by multiple samplings, 5 to 8 per kidney, in normal, hydropenic, Munich-Wistar rats. Single nephron filtration rate (SNGFR) measurements served as an independent marker of internephron heterogeneity. Whether derived as SNFFALB or SNFFHCT, a wide degree of internephron variability in SNFF, comparable to that found for SNGFR (P > 0.2) was observed in all kidneys. Hematocrit-derived SNFF values, however, were some 80% higher than those obtained with 125I albumin (SNFFHCT 0.447 plusminus SEM 0.016 versus SNFFALB 0.258 plusminus 0.009, P < 0.001). The disparity in results obtained by the two methods disappears if the efferent arteriolar hematocrit (Hctg) is assigned a value 17 plusminus SEM 1.4% higher than the corresponding femoral arterial hematocrit and might well be a reflection of the perfusion of superficial glomeruli with erythrocyte rich blood produced by the "plasma-skimming" phenomenon. The data suggest that multiple estimates of SNGFR and SNFF in a given rat kidney are needed to provide representative mean values for glomerular dynamic studies.

Hétérogénéité internéphrons de la filtration fraction et disparité entre les valeurs dérivées des concentrations de protéine et d'hématocrite. La variabilité de la fraction de filtration des néphrons individuels (SNFF) et la relation entre les fractions de filtration déterminées simultanément à partir de 125I albumine (SNFFALB) et de l'hématocrite (SNFFHCT) ont été évaluées par des prélèvements multiples, 5 à 8 par rein, chez des rats Munich-Wistar normaux, hydropéniques. La mesure du débit de filtration glomérulaire des néphrons individuels (SNGFR) a servi de marqueur indépendant de l'hétérogénéité entre les néphrons. Qu'elle soit calculée à partir de SNFFALB ou de SNFFHCT la fraction de filtration des néphrons individuels a mis en évidence une variabilité internéphrons importante, comparable à celle observée pour SNGFR (P < 0, 2), dans tous les reins. Les valeurs de SNFF dérivées de l'hématocrite étaient cependant de 80% supérieures à celles obtenues à partir de 125I albumine (SNFFHCT 0,447 plusminus SEM 0,016 vs SNFFALB 0,258 plusminus 0,009, P < 0,001). La disparité des résultats obtenus par les deux méthodes est effacée si l'hématocrite de l'artériole afférente (Hctg) reçoit une valeur de 17 plusminus SEM 1,4 pour cent supérieure à celle de l'hématocrite correspondant de l'artère fémorale, ce qui peut être le reflet de la perfusion des glomérules superficiels par un sang enrichi en globules rouges du fait du phénomène d'écrémage. Les résultats suggèrent que des estimations multiples de SNGFR et de SNFF pour un rein de rat donné sont nécessaires afin de fournir une moyenne représentative dans les études de dynamique glomérulaire.

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