AJP - Regulatory, Integrative and Comparative Physiology, Vol 258, Issue 6 1313-R1319, Copyright © 1990 by American Physiological Society
Measurements of blood flow to individual glomeruli in the ophidian kidney
S. D. Yokota and W. H. Dantzler
Department of Physiology, West Virginia University School of Medicine, Morgantown 26506.
Continuous measurements of the instantaneous rate of blood flow to
individual glomeruli in a normal vertebrate kidney were made in the garter
snake Thamnophis sirtalis. Epifluorescence video microscopy was used to
visualize and record blood flow in the afferent arterioles of superficial
nephrons. The dual-slit method was used for the determination of red blood
cell (RBC) velocity from the video replay. Simultaneous measurements of the
vessel diameter allowed the continuous determination of the instantaneous
rate of blood flow. A total of 100 glomeruli was surveyed in 12 animals.
These glomeruli displayed both constant and highly variable rates of blood
flow, with 21% of all nephrons displaying intermittent glomerular
perfusion. The mean single-nephron blood flow rate (SNBFR) for all
individuals was 23.9 +/- 10.3 (SD) nl/min (n = 12). The percentage of
nephrons with intermittent flow for an individual animal increased
significantly with increasing plasma osmolality. Intermittency was
associated with low SNBFR values; SNBFR averaged 13.5 +/- 10.2 (SD) nl/min
(n = 21) in intermittent nephrons and 29.2 +/- 19.0 (SD) nl/min (n = 79) in
continuous flow nephrons, the difference being significant (P less than
0.001). Nephrons with continuous perfusion displayed a much greater range
of SNBFR values than intermittent nephrons. This suggests that, although
changes in whole kidney glomerular filtration rate (GFR) in reptiles need
not involve glomerular intermittency, intermittency may lower GFR.
