AJP - Regulatory, Integrative and Comparative Physiology, Vol 254, Issue 6 1007-R1010, Copyright © 1988 by American Physiological Society
Fetal thoracic duct lymph flow response to intravascular saline infusion
R. A. Brace
Department of Reproductive Medicine, University of California, San Diego, La Jolla 92093.
The left thoracic lymph duct was catheterized at the base of the neck in
the sheep fetus at 123-136 days of gestation, and the lymphatic catheter
was connected to a jugular vein catheter so that the lymph could return to
the fetus. Lymph flow was studied 5 days after catheter implantation in the
unanesthetized fetus. Basal fetal thoracic duct lymph flow rate per unit
body weight averaged three times adult sheep values. After an infusion of
20 ml/kg of warmed isotonic saline into a fetal vein over 5 min, lymph flow
rate increased significantly to 161 +/- 15% of control, with a peak at 8
min after termination of the infusion, and flow declined thereafter. The
increased lymph volume above baseline values over 30 min averaged 5.7% of
the infused volume and is similar to the adult response. Plasma and lymph
protein concentrations decreased as did the lymph-to-plasma protein
concentration ratio. The latter is opposite to what occurs in the adult
under the same conditions. Thus the present study shows that even though
the fetus has a much higher basal thoracic duct lymph flow rate than the
adult, the responsiveness of the fetal lymphatic system to intravascularly
infused saline is similar to that of the adult. The decrease in the
lymph-to-plasma protein concentration ratio suggests that there may be
differences between fetal and adult vascular-interstitial-lymphatic protein
kinetics.
