[Aging of nervous system and S-100 proteins]

Recently, the human gene encoding the beta subunit of S-100 protein (S-100 beta) has been mapped on the long arm of chromosome 21 (21q, 22), where the locus of Down's syndrome (DS) is present. We determined the concentrations of S-100 proteins (alpha and beta) together with Cu/Zn-superoxide dismutase (SOD), a well-known marker protein of chromosome 21, in the blood samples of patients with Down's syndrome by means of sensitive immunoassay methods. S-100 beta and SOD concentrations in blood plasma and lymphocyte fractions of the patients were enhanced, while S-100 alpha concentrations in the same samples showed levels similar to those of control subjects. These results indicate that the gene-dosage effect of S-100 beta is expressed in patients with trisomy of chromosome 21. Concentrations of several proteins related to nervous tissues (S-100 alpha, S-100 beta, SOD, alpha-enolase, gamma-enolase, and G-proteins, Go alpha, Gi2 alpha G beta) in the brains of rats aged 2 to 30 months and in the human cerebral cortices obtained at autopsy were immunoassayed. It was found that S-100 beta concentrations in rat brains increased with age solely in the cerebral cortex, but there was little increase or decrease in the levels of SOD and other proteins. S-100 beta levels in human cerebral cortices showed a tendency similar to those of rat cerebral cortices; S-100 beta concentrations in the aged cerebral cortices were significantly higher than those of young adults.(ABSTRACT TRUNCATED AT 250 WORDS)