The permeability of the blood-brain barrier to protein in the post-hypoxic cerebral edema of the rat.

The permeability of the blood-brain barrier to protein was studied in the post-hypoxic cerebral edema of rats, using horseradish peroxidase (HRP) as a tracer protein. Under halothane anesthesia, HRP was injected intravenously. Then the animals were exposed to hypoxic-ischemia by inhalation of 5% oxygen in nitrogen and temporary occlusion of the left common carotid artery for 10-30 min. Twenty-four, 48 or 72 h after the hypoxic experiments, the animals were anesthetized with sodium pentobarbital and their body tissues were fixed by perfusion with a mixture of glutaraldehyde and p-formaldehyde before the autopsy. No brain edema was observed in the animals exposed to hypoxia for 10 min, but the animals exposed to hypoxia for 20-30 min revealed a left hemispheric brain edema. The brain was immediately immersed in the same fixatives, and then sectioned with a cryostat. The sections were stained histochemically according to the method of Graham and Karnovsky (1966) to identify the distribution of the HRP. HRP was not found even in the edematous hemisphere. In this type of brain edema, it is suggested that there was no acceleration of permeability of blood-brain barrier to serum proteins whose molecular weights were larger than HRP, and therefore it would have no causative relationship with the production of brain edema.