Evaluation of BBB damage in an UV irradiation model by endogenous protein tracers

Autologous serum proteins have proved to be suitable tracer to evaluate vascular permeability. The dynamic behaviour of anti-HRP immunoglobulins was studied in ultraviolet (UV) irradiation induced brain edema. Cerebral cortex of 36 anaesthetized adult rats was irradiated following a 2 x 2 mm parietal craniotomy. Immunization was carried out by 3 subcutaneous injections of 10 mg HRP in 0.5 ml complete freund adjuvant (CFA), 6, 4 and 2 weeks before the injury. Control animals were immunized only with CFA; further control animals were operated and irradiated without any previous immunization. After survival times ranging from 30 min to 24 hours, postoperation animals were transcardially perfused with 4% fresh paraformaldehyde solution in phosphate buffered saline. After postfixation at 4 degrees C, 20 microns vibratome sections were prepared for incubation with a solution of 0.05% HRP, washed and developed by the DAB reaction. The reactions showed a remarkable exsudation and spreading of anti-HRP antibodies in the edematous brain. The antigen-antibody reaction was conspicuous in animals with shorter survival periods in the necrotic area and near the lesion (1-2 mm). After a longer survival time extravasation involved the whole hemisphere. In animals with the longest survival period labeled serum proteins were found even in the white matter of the hemisphere contralateral to the injury. Endogenous tracer of BBB function is useful to study the spreading of brain edema in a delayed time after the edematous lesion.