The effect of dexamethasone on serum protein extravasation and edema development in experimental brain tumors of cat

Abstract

Experimental brain tumors were produced in 20 cats by stereotaxic xenotransplantation of a blastomatous glial cell clone into the internal capsule of the left hemisphere. Ten of these animals were treated after 2 weeks with a single injection of 10 mg dexamethasone in crystalline suspension. Three weeks after xenotransplantation vascular permeability was studied by electron microscopy with horseradish peroxidase as the barrier tracer (four animals), and extravasation of serum proteins was visualized by immunohistochemistry, using an image processing system (16 animals). In animals used for immunohistochemistry, the water content of peritumoral brain tissue was also determined. In both treated and untreated animals, spherical tumors with a diameter of about 10 mm were present at the implantation site. Extravasation of horseradish peroxidase was detected only in the tumor, but there was accumulation of serum proteins both in the tumor and the peritumoral white matter. Edema, in consequence, originated mainly in the tumor from where it spread into the surrounding brain tissue. Corticosteroid therapy reduced the water content of peritumoral brain tissue but did not affect increased barrier permeability of tumor vessels, and only slightly improved peritumoral accumulation of serum proteins. It is concluded that amelioration of tumor edema by corticosteroids cannot result solely from tightening of the blood-brain barrier to circulating macromolecules but must be due to an active restoration of cerebral water homeostasis despite persisting serum protein extravasation.

Effects of glucocorticoid and chemotherapy on the peritumoral edema and astrocytic reaction in experimental brain tumor

“…The extravasated serum albumin is supposed to spread into the surrounding brain [1], and its distribution is expected to correlate with the extent of edema. Thirdly, the astrocytic reaction was examined to evaluate the histologic alterations of the brain since astrocytes are known to react nonspecifically but sensitively to various kinds of pathologic conditions [2][3][4][5][6][7].…”

T1 snapshot flash measurement of rat brain glioma: kinetics of the tumor‐enhancing contrast agent manganese (iii) tetraphenylporphine sulfonate

“…Cryostat sections of the frozen brains and paraffin sections of the formalinfixed brains were prepared in the horizontal plane and stained with hematoxylin and eosin, cresyl violet, and luxol fast blue. Peritumoral edema was visualized by immunohistochemistry of extravasated serum immunoglobulins, as described elsewhere ( 7).…”

The pathophysiology of experimental brain edema

“…Increased barrier permeability in the tumor is visualized by intravenous injection of Evans blue. Note swelling of the ipsilateral hemisphere with shift of the midline to the opposite side and absence of Evans blue extravasation in peritumoral white matter (from [17]). magnetic resonance imaging.…”

“…One week after the intramuscular injection of a cristalline suspension of 10 mg/ kg dexamethasone, water and electrolyte content of peritumorous edema return to close to, and blood flow even above, normal. Surprisingly, this intervention does not reduce the increased barrier permeability of tumor vessels to intravascular tracers such as Evans blue and horseradish peroxidase, and it only slightly reduces peritumorous accumulation of serum proteins [17] (Figure 9). This demonstrates that corticosteroids do not alleviate tumor edema by a tightening of the bloodtumor barrier to circulating macromolecules; they actively restore cerebral water and ion homeostasis.…”