Kinetics of semax penetration into the brain and blood of rats after its intranasal administration

The radioactive petide analogue Semax corresponding to the ACTH(4–10) sequence (Met-Glu-His-Phe-Pro-Gly-Pro) with a specific radioactivity of 56 Ci/mmol labeled with tritium at the C-terminal Pro was prepared. The labeled peptide was used for studying the kinetics of Semax penetration into rat brain and blood after its intranasal administration (50 μg/kg, 20 μl of solution) to nonbred white rats of body mass 200–250 g. It was demonstrated that 0.093% of the total introduced radioactivity per gram can be found in the rat brain 2 min after the administration, 80% of this radioactivity belonged to Semax, and the rest, to its metabolites. The peptide undergoes rapid enzymatic degradation, with the tripeptide Pro-Gly-Pro prevailing in biological samples relative to the total content of Semax and its metabolites.