Immunohistochemical expression of glutathione S-transferase placental type (GST-pi), a detoxifying enzyme, in normal arachnoid villi and meningiomas.

Human normal dura mater containing arachnoid villi were examined for their expression of glutathione S-transferase placental type (GST-pi), a detoxifying enzyme, using an immunohistochemical method. All of the arachnoid villi and arachnoid cells in five normal cases were found to have expression of GST-pi, although no positive reaction for the enzyme was present in other tissues of the dura mater. The results show a possible role for arachnoid tissues in protecting human brain from hazardous xenobiotics in the cerebrospinal fluid. Twenty-six meningiomas were also examined for expression of the enzyme. Tissues of meningotheliomatous meningiomas were always positive for expression of the enzyme. Transitional meningiomas also showed the expression in their meningotheliomatous components. No staining reaction of GST-pi was recognized in fibroblastic meningiomas except for two cases with a tendency to meningotheliomatous differentiation. The findings suggest a functional similarity between the arachnoid tissues and meningotheliomatous components of meningiomas.