[Quantitative determination of neurospecific protein S-100 in mouse brain cortical synaptosomes]

Using monospecific antibodies against protein S-100 labelled with horseradish peroxidase (a-S-100-HP) or iodine (a-S-100-125I) two types of protein S-100 bound to the synaptosomal membrane were obtained. The first type accessible for a-S-100-HP (6.4% of total protein S-100 in the synaptosomes) and the second type accessible for a-S-100-125I (22.4%) differ in their location on the membrane surface. The total content of protein S-100 in the synaptosomes determined by solid phase radioimmune analysis is 284 +/- 0.84 ng per mg of total synaptosomal protein. Coprecipitation of the protein with the synaptosomal fraction is insignificant. After treatment of the synaptosomal membranes with 1% glutaric aldehyde or 4% paraformaldehyde, 20 and 50% of membrane-bound protein S-100 are found in the synaptosomal membrane, respectively. The immunohistochemical localization of protein S-100 in synaptosomes was established.