Regulation of microvascular filtration in the myocardium by
interstitial fluid pressure.
Stewart, Randolph H., Douglas A. Rohn, Uwe Mehlhorn, Karen L. Davis,
Steven J. Allen, and Glen A. Laine.
Department of Veterinary Physiology and Pharmacology, Texas A&M
University, College Station, TX, 77843 and Center for Microvascular
and Lymphatic Studies, Department of Anesthesiology, The University
of Texas Medical School, Houston, TX, 77030
APStracts 3:0243R, 1996.
We hypothesized that myocardial microvascular filtration rate (JV)
could be manipulated by varying end-diastolic myocardial interstitial
hydrostatic (PINT) pressure. Dogs under general anesthesia were
instrumented with intramyocardial capsules to measure PINT and with
prenodal myocardial lymphatic trunk cannulae and superior vena caval
balloon-tipped catheters to manipulate myocardial lymph flow.
Because, for a given surface area, the lymph to plasma protein
concentration ratio (CL/CP) varies inversely with microvascular
filtration rate (JV), CL/CP was utilized as an index of changes in
JV. When lymphatic outflow pressure (P0) was elevated to abolish
lymph flow and force myocardial interstitial fluid volume to expand,
PINT rose significantly from 15.0 +/- 0.8 to 27.6 +/- 1.0 mmHg and
CL/CP increased significantly from 0.75 +/- 0.04 to 0.85 +/- 0.04,
indicating a decrease in JV. When P0 was lowered and lymph flow
resumed, PINT and CL/CP decreased significantly to 15.3 +/- 0.9 mmHg
and 0.75 +/- 0.04, respectively, indicating an increase in JV. We
conclude that myocardial microvascular filtration rate may be
modulated by changes in PINT resulting from alterations in myocardial
interstitial fluid volume secondary to variations in lymph flow from
the heart.
Received 1 August 1995; accepted in final form 3 June 1996.
APS Manuscript Number R483-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 4 July 96