Regulation of microvascular filtration in the myocardium by interstitial fluid pressure
Stewart, R.H.; Rohn, D.A.; Mehlhorn, U.; Davis, K.L.; Allen, S.J.; Laine, G.A.
American Journal of Physiology 271(6 Pt 2): R1465-R1469
1996
ISSN/ISBN: 0002-9513 PMID: 8997340 Document Number: 459077
We hypothesized that myocardial microvascular filtration rate (J-V) could be manipulated by varying end-diastolic myocardial interstitial hydrostatic (P-int) pressure. Dogs under general anesthesia were instrumented with intramyocardial capsules to measure P-int and with prenodal myocardial lymphatic trunk cannulas 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 (C-L/C-P) varies inversely with J-V, C-L/C-P was utilized as an index of changes in J-V. When lymphatic outflow pressure (P-o) was elevated to abolish lymph flow and force myocardial interstitial fluid volume to expand, P-int rose significantly from 15.0 +- 0.8 to 27.6 +- 1.0 mmHg and C-L/C-P increased significantly from 0.75 +- 0.04 to 0.85 +- 0.04, indicating a decrease in J-V. When P-o was lowered and lymph flow resumed, P-int and C-L/C-P decreased significantly to 15.3 +- 0.9 mmHg and 0.75 +- 0.04, respectively, indicating an increase in J-V. 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.