Quantitative Spectrophotometric Microplate Assay for Angiotensin-converting Enzyme in Cerebrospinal Fluid

studies using clinical and/or experimental approaches will address this hypothesis, regarding which little infor- mation is currently available. Similarly, we have no useful information at present regarding possible interactions between S100B and sex hormones, which could also be hypothesized on the basis of the gender differences found in S100B concentrations. More generally, the growing body of evidence that indicates a biological role of S100B as a cytokine points to the usefulness of future studies on possible interactions between this protein and individual hormonal patterns. The most probable origin of S100B in peripheral blood, as previously reported in several studies, is nervous tissue, although we cannot exclude the possibility that it may also be released from other sites of concentration, such as adipose tissue (20 ). However, data on the pres- ence of the protein in adipose tissue at the ages studied here are not conclusive. Finally, the different peaks of protein concentration in the two sexes could, in common with other clinical and anthropometric studies (i.e., height/weight growth refer- ence curves), suggest the possibility that brain maturation in the pediatric period differs in males and females, as it does in the intrauterine and adult periods (9, 21 ). In this respect it could be relevant that genetically modulated overexpression of S100B has been reported to affect the behavior of female mice without causing any appreciable effects in males in experimental models (22 ). In conclusion, the reference curve for S100B protein in peripheral blood in healthy pediatric patients constitutes a useful tool to evaluate pathologic alterations of the protein during this period and also suggests an approach for future investigations into the suggested neurotrophic role of the protein, which could potentially be related to the process of maturation, including hormone concentra- tions.