AJP - Regulatory, Integrative and Comparative Physiology, Vol 266, Issue 3 709-R713, Copyright © 1994 by American Physiological Society
Blood volume response to drainage of left thoracic duct lymph in the ovine fetus
R. A. Brace
Department of Reproductive Medicine, University of California at San Diego, La Jolla 92093-0803.
Although it is known that left thoracic duct lymph flow rate in the ovine
fetus is several times that in the adult relative to body weight, the role
of the lymphatic system in maintaining fetal blood volume has not been
explored. In the present study, the left thoracic lymph duct was drained
without return to the fetal circulation in 10 chronically catheterized
animals for 7 h. Four experiments in which the lymph was returned to the
circulation served as control. During the 7-h drainage, the total volume
drained was 174.4 +/- 19.6 ml. Thoracic duct lymph flow rate decreased
gradually and averaged 22.2 +/- 3.4% (SE) below control at 6-7 h compared
with a small increase in the control experiments (analysis of variance: P =
0.0013 comparing 2 groups). Fetal blood volume decreased (P < 0.0001) by
8.2 +/- 1.1% at 3 h because of a decrease in plasma volume with a further
small decrease in blood volume to 9.7 +/- 0.9% below normal at 7 h. The
decreases in blood volume at 1, 3, 5, and 7 h were 49.5, 40.2, 24.6, and
21.7%, respectively, of the volume of lymph that was drained. Fetal
vascular pressures and heart rate did not change significantly. Although
protein concentrations in plasma (-6.8 +/- 1.3%) and lymph (-7.5 +/- 2.1%)
decreased, the lymph-to-plasma protein concentration ratio remained
constant at 0.72 +/- 0.01.(ABSTRACT TRUNCATED AT 250 WORDS)
