INTERSTITIAL FLUID PRESSURE IN DMBA-INDUCED RAT MAMMARY-TUMORS

Abstract

Interstitial fluid pressure (IFP) in DMBA[dimethybenz[a]anthracene]-induced rat mammary tumors was measured by micropuncture with sharpened glass capillaries (diameter 1-3 .mu.m) and by the wick-in-needle technique (WIN). IFP in the superficial layers of the tumors (depth < 800 .mu.m) was measured with micropuncture whereas WIN was used for measurements in deeper areas. IFP in the superfical layers of the tumors was 2.4 mm Hg (SD 2.4, n = 19), while IFP in deeper layers increased with increasing tumor weight. Thus, central IFP in tumors weighing > 5.5 g was 16.0 mm Hg (SD 4.8, n = 10), with a maximum value of 23.3 mm Hg. When related to tumor histopathology a significant correlation was found between high cellular differentiation (i.e., low degree of malignancy) and high interstitial fluid pressure only. The high IFP may be secondary to a high capillary protein permeability and/or a relatively insufficient lymphatic drainage. A further rise in IFP might result from ischemic cell swelling and/or a continuous cell proliferation within a tissue of rather low compliance. Together or alone, one or more of these factors could facilitate the development of a compartment syndrome with concomitant cell death and tissue necrosis.