AJP - Renal Physiology, Vol 243, Issue 1 96-101, Copyright © 1982 by American Physiological Society
Effects of saline on continuously recorded filtration fractions in cat kidney
S. N. Rasmussen and O. I. Nissen
The radioactivity of [51Cr]EDTA and [125I]albumin in arterial and in deep
and superficial renal venous blood was continuously measured in an
extracorporeally recirculating system. The filtration fraction of plasma in
the superficial (FFs) and in the deep (FFD) venous drainage area was
computed every 100 s. Following infusion of Ringer fluid a decrease in the
FFD/FFs ratio was observed--mainly due to a fall in FFD. The decrease in
the FFD/FFs ratio was more pronounced with infusion of Ringer fluid
directly into the renal artery than with infusion at the same rate (1.0-1.5
ml . min-1) into a jugular vein, showing that a direct renal effect is
involved. The sensitivity of the FFD/FFs reaction is high, as the fluid
loads given were moderate. The fall in FFD may be due to a preferential
increase in medullary blood perfusion, which, by wiping out the medullary
hyperosmolality, promotes diuresis.
