Diabetes, Vol 42, Issue 5 720-731, Copyright © 1993 by American Diabetes Association
Thoracic duct lymph. Relative contribution from splanchnic and muscle tissue
GM Steil, MA Meador and RN Bergman
Department of Physiology and Biophysics, University of Southern California Medical School, Los Angeles 90033.
We have shown previously that thoracic duct lymph insulin dynamics are well
correlated with tracer-determined whole-body glucose uptake and have
suggested that thoracic duct lymph insulin is representative of insulin
concentration in muscle interstitial fluid. However, thoracic duct lymph is
comprised of interstitial fluid from all sub-thoracic tissue beds. To
investigate the relative contribution of muscle interstitial fluid to total
thoracic duct lymph flow, the distribution and elimination of [14C]inulin
was investigated in eight experiments with conscious dogs. Both plasma and
thoracic duct lymph were measured, and a three-compartment model that was
hypothesized to consist of plasma, splanchnic interstitial fluid, and
muscle interstitial fluid was identified. Identifications were performed
with either a bolus protocol (n = 4) or an infusion protocol (n = 4), and
the predicted [14C]inulin dynamics in the splanchnic and muscle
interstitial fluid compartments were compared with measured values in
thoracic duct lymph. Neither compartment predicted the thoracic duct
[14C]inulin dynamics; however, a model based on a percentage contribution
from each tissue bed fit the thoracic data well. The relative contribution
of splanchnic interstitial fluid to the total thoracic duct lymph flow
averaged 78 +/- 5% for the bolus protocol and 54 +/- 5% for the infusion
protocol. Thus, we conclude that in the conscious animal, approximately
25-50% of thoracic duct lymph originates from muscle interstitial fluid.