Thoracic duct lymph flow in pregnant sheep and response to blood volume expansion

Left thoracic duct lymph flow rate averaged 0.077 +/- 0.003 (SD) and 0.078 +/- 0.003 ml X min-1 X kg-1 in near-term pregnant and nonpregnant sheep (P greater than 0.5). Lymph and plasma protein concentrations were unaltered in the pregnant compared with the nonpregnant animals. The thoracic duct lymph flow responses to three serial intravenous infusions of lactated Ringer solution were essentially the same in the pregnant and nonpregnant animals. Blood volume and vascular pressure changes during and after volume loading were essentially the same in both groups. In addition, terbutaline administration after volume loading caused no change in thoracic duct lymph flow rates. Thus the present study suggests that basal lymph flow rates, lymphatic function, and vascular as well as interstitial compliances are largely unaltered late in pregnancy in the sheep. In addition, beta-mimetic stimulation with terbutaline does not appear to suppress lymph flow rate.