AJP - Heart and Circulatory Physiology, Vol 256, Issue 1 16-H20, Copyright © 1989 by American Physiological Society
Thoracic duct lymph flow and its measurement in chronically catheterized sheep fetus
R. A. Brace
Department of Reproductive Medicine, University of California, San Diego, La Jolla 92093.
A method was developed for chronic catheterization of the left thoracic
lymph duct at the base of the neck in the sheep fetus, which did not
disrupt the other major lymphatic vessels that join the venous circulation
at the same location. The lymphatic catheter was connected to a catheter in
a jugular vein when lymph flow was not being recorded, so that the lymph
continuously returned to the fetal circulation. Special consideration of
catheter size to minimize flow resistance and treatment to prevent clotting
were required. Individual animals were maintained up to 17 days with lymph
flow continuing. In 13 fetuses averaging 128 days gestation (term = 147
days) at the time of catheterization, lymph flow rate was measured for 1 h
each day for the first 7 postsurgical days with an on-line computer
technique that continuously calculated lymph flow rate. Lymph flow averaged
0.64 +/- 0.17 (SD) ml/min in fetuses weighing 2.3-4 kg and tended to
undergo a nonsignificant increase with time. Lymph and plasma protein
concentrations did not change with time. In individual fetuses, large
spontaneous variations in lymph flow rate occurred over periods of several
seconds to a few minutes. Analysis showed that these variations in flow
rate were not associated with fetal breathing movements. Thus the present
study describes a technique for studying the dynamics of lymph flow in the
unanesthetized sheep fetus in utero over a time period limited primarily by
the length of gestation. In addition, it appears that thoracic duct lymph
flow rate in the fetus per unit body weight averages three to four times
that in the adult.
