AJP - Renal Physiology, Vol 249, Issue 1 132-F138, Copyright © 1985 by American Physiological Society
Dynamics of glomerular filtration in the river lamprey, Lampetra fluviatilis L
A. J. McVicar and J. C. Rankin
Hydrostatic pressures decreased in the dorsal aorta (from 21.6 +/- 2.0 to
18.7 +/- 0.2 mmHg), proximal (from 19.5 +/- 1.6 to 16.2 +/- 1.7 mmHg) and
distal (from 16.7 +/- 0.7 to 13.2 +/- 0.9 mmHg) renal arteries, and
glomerular capillaries (from 16.1 +/- 1.1 to 12.3 +/- 0.6 mmHg) of
anesthetized lampreys transferred from freshwater to isosmotic 20-30%
seawater. Maximal vascular resistance appeared to be in the efferent
arteriole; there was a 67% decrease in pressure between glomerular and
peritubular capillaries. Plasma oncotic pressure was unchanged. The
calculated afferent effective filtration pressure decreased by 87% after
transfer and showed a good correlation with single nephron filtration rate.
Effective renal plasma flow was high but variable in freshwater lampreys
and decreased by 84% after transfer, but glomerular filtration rate did not
decrease proportionately and there was a nonsignificant increase in mean
filtration fraction from 0.045 +/- 0.022 to 0.080 +/- 0.021. Calculation of
glomerular efferent oncotic pressure indicated that filtration equilibrium
did not exist in freshwater lampreys but was attained after transfer. The
mean coefficient of filtration of freshwater lampreys was 0.028 +/- 0.002
nl X s-1 X mmHg-1.
