AJP - Renal Physiology, Vol 267, Issue 3 423-F427, Copyright © 1994 by American Physiological Society
Glomerular hemodynamics in cell-free and erythrocyte-perfused isolated rat kidney
F. B. Gabbai, O. W. Peterson, S. Khang, C. B. Wilson and R. C. Blantz
Division of Nephrology-Hypertension, University of California, San Diego, School of Medicine 92161.
The cell-free isolated perfused kidney (IPK) is characterized by normal
glomerular filtration rate (GFR) and very low filtration fraction (FF).
Addition of erythrocytes to the perfusate (IEPK) increases FF while
maintaining "normal" GFR levels. Micropuncture studies were performed in
IPK and IEPK to establish the determinants of the glomerular
ultrafiltration process responsible for low FF in IPK and to evaluate the
impact of the addition of erythrocytes on these determinants. Nephron
filtration rate was similar in IPK and IEPK (40 +/- 4 vs. 39 +/- 4 nl/min),
whereas nephron perfusate flow was significantly higher in IPK (1,247 +/-
100 vs. 112 +/- 13 nl/min), leading to a superficial nephron FF of 3.4 +/-
0.2% in IPK and 36 +/- 2% in IEPK. Glomerular hydrostatic pressure (PG) and
transcapillary hydrostatic pressure gradient (delta P) were 53 +/- 2 and 33
+/- 1 mmHg, respectively, in IPK and 51 +/- 3 and 34 +/- 2 mmHg in IEPK,
all normal values. Glomerular arteriolar resistances were significantly
lower in IPK than in IEPK, and the glomerular ultrafiltration coefficient
(LpA) was significantly lower in IPK (0.053 +/- 0.010 vs. 0.100 +/- 0.020
nl.s-1.mmHg-1), but both values are within the normal in vivo range. These
results demonstrate that low FF in IPK is not due to decreased delta P or
LpA values but to the high renal perfusion rate required to maintain normal
PG and delta P values. Addition of erythrocytes increases glomerular
arteriolar resistances and restores glomerular hemodynamics to a pattern
nearly identical to in vivo conditions.(ABSTRACT TRUNCATED AT 250 WORDS)
