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

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Abstract
To study the effects of glucocorticoids and chemotherapeutic agents on the pathophysiology of the tumor-induced brain edema, the site of Evans blue-albumin extravasation, the distribution of extravasated serum albumin, and the extent of local astrocytic reaction were examined in a rat model of implanted brain tumor. Experimental brain tumors were produced by implanting small pellets of Walker 256 carcinosarcoma into the cerebral cortex of Wistar rats. In the steroid group, rats were administered with intraperitoneal methylprednisolone succinate (15 mg/kg) daily on and after the 6th day postimplantation, and sacrificed on the 14th day. In the chemotherapy group, rats were given an intravenous injection of cyclophosphamide (30 mg/kg) on the 14th day, and sacrificed on the 21st day. Rats in the untreated group were sacrificed on the 14th day without any therapy. Each animal was sacrificed by the transcardiac perfusion with paraformaldehyde 30 min after intravenous injection of Evans blue. Firstly, coronal blocks of the brain were examined for Evans blue staining macroscopically. Paraffin embedded sections were studied for the Evans blue fluorescence and for the immunohistochemical reaction to serum albumin and GFAP. The examination of Evans blue demonstrated that the origin of extravasation of serum albumin was the tumor and the adjacent brain with dense tumor cell infiltration in any group of rats. The extravasated serum albumin distributed widely and the astrocytic reaction was prominent in the brain of the untreated group. A positive correlation was observed between the intensity of albumin immunoreaction and the degree of astrocytic proliferation. Chemotherapy effectively decreased the size of tumor and reduced the extravasation of serum albumin. The astrocytic reaction was however, not reduced. In the steroid group, the size of tumor was not significantly affected but the albumin extravasation as well as astrocytic reaction was markedly reduced. It was concluded that glucocorticoid is an effective drug against tumor-induced brain edema, which not only reduces the extravasation of serum components but also prevents histologic alterations of the brain.