AJP - Renal Physiology, Vol 248, Issue 6 851-F857, Copyright © 1985 by American Physiological Society
Effects of Ringer fluid on regional blood flow and filtration rate in the cat kidney
S. N. Rasmussen, J. S. Andersen and O. I. Nissen
The larger subcapsular veins of the in situ cat kidney were cut open near
the hilus and occluded between the slits and the common renal vein, thus
permitting separation and direct measurement of venous outflows from the
superficial (outer cortex) and deep (inner cortex plus medulla) drainage
area. The direct recording of venous outflow in the two areas combined with
plasma inulin and protein analyses provided consecutive determinations of
the rate of glomerular filtration and arterial inflow of both areas. Our
primary result is the demonstration of a regional difference in the renal
response to extracellular isotonic volume expansion. Infusion of Ringer
fluid at a moderate rate (1.0-2.0 ml X min-1) increased both blood flow
(RBF) and glomerular filtration rate (GFR) in both areas; however, the RBF
response was proportionately greater in the deep area and the GFR response
was proportionately greater in the superficial area. Compared with a
noninfused control series, statistically significant differences occurred
after about 1 h of infusion. After 80 min, average RBF had increased by 33
and 20%, while average GFR had increased by 31 and 54% in the deep and in
the superficial areas, respectively. To reveal direct renal effects of the
Ringer fluid, the site of infusion was shifted alternately between the
renal artery and the jugular vein. The results suggest that the changes in
blood flow are elicited indirectly by neural or humoral mechanisms.
