AJP - Renal Physiology, Vol 269, Issue 5 628-F636, Copyright © 1995 by American Physiological Society

ARTICLES

Cross-linked hemoglobin increases fractional reabsorption and GFR in hypoxic isolated perfused rat kidneys

A. D. Baines, B. Christoff, D. Wicks, D. Wiffen and D. Pliura
Department of Clinical Biochemistry, University of Toronto, Ontario, Canada.

We compared the ability of human red blood cells (RBC) and a cell-free oxygen carrier to maintain isolated perfused kidney function under moderately hypoxic conditions. Recirculating perfusate was gassed initially with 93% air-7% CO2, and, after 30 min, the gas was changed to 12 O2-7 CO2-81% N2. Oxygen content of the perfusate was increased with RBC (30 g/l Hbg) or highly purified human hemoglobin Ao (HbAo) polymerized with O-raffinose (o-R-poly-Hb, 30 g/l Hbg). For comparison, kidneys were perfused with 60 g/l of bovine serum albumin (BSA) alone. The effects of unmodified hemoglobin were examined by adding 5 g/l of nonpolymerized HbAo to the BSA perfusate after 20 min. The effect of increasing oxygen delivery without hemoglobin was examined by switching to 93% O2 after 20 min during some BSA perfusions (BSA-HiO2). Vascular resistance decreased progressively in o-R-poly-Hb- and BSA-HiO2-perfused kidneys but remained constant in other experiments. Nitro-L-arginine methyl ester (L-NAME) prevented vasodilation and increased the filtration fraction of o-R-poly-Hb-perfused kidneys with no change in other functions. L-NAME also prevented the formation of methemoglobin. After a 70-min perfusion with BSA, Na reabsorption was 82 +/- 3% (means +/- SD), and inulin clearance [glomerular filtration rate (GFR)] was 0.66 +/- 0.33 ml.min-1.g-1. RBC increased reabsorption to 95% (85-98%) (median, 25th-75th percentile) but did not alter GFR (0.52 +/- 0.26 ml.min-1.g-1). o-R-poly-Hb increased Na reabsorption proportionately more than GFR, so that, while GFR was doubled to 1.04 +/- 0.40 ml.min-1.g-1, Na reabsorption increased to 98% (92-99.5%). HbAo increased GFR to 1.07 +/- 0.44 ml.min-1.g-1 and increased reabsorption to 89 +/- 6%.(ABSTRACT TRUNCATED AT 250 WORDS)

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