Introduction: Albumin seems to be the most effective Scavanger-antioxidant in cerebrospinal fluid (CSF). It is probably able to protect the brain area against free radical activity even if the blond brain barrier (BBB) is damaged by various types of neurological diseases. Its antioxidant capacity along with vitamin C is responsible for the observed and described absence of free radicals in CSF. Material and Method: The total amount of 30 (15F/15M) patients suffering from various neurological diseases was divided finto two groups. Based on the Q = Alb (CSF)/Alb (S) the hrst group consists of probands with damaged BBB (GP). In the second ope were persons with hitherto physiological function of BBB (GF). Beside determination of other acute phase proteins, the serum albumin was estimated by two independent methods. For the common measurement of serum albumin concentration served the spectrophotometric method (Synchron apparatus) which was supplied by the immunoturbidimetry (BN II Behring). The use of two measurements of each serum sample was caused by the previous observed phenomena: in the tase of a disbalance between free radical (FR) concentration and total antioxidant capacity of the organism higher values of albumin were found by immunoturbidimetric estimation, compared to spectrophotometry, in the same serum samples. The CSF-albumin was estimated, however, ohly by immunoturbidimetry. Free radical concentration was measured by the original spectrophotometric method based on the chlorophylline reaction in serum ohly, because any FR in CSF were found. Results: The obtained values of albumin estimation demonstrate our predispositions. GP group: Albumin in serum: spectrophotometrically: 36.7 x 4.S gn* turbidimetrically: 40.2 x 7.5 g/1 Albumin in CSF(only turbidimetrically): 439.4 x 1012 mg/1** Free radicals in serum: 2.55 x 0.23 mg Fe2+** GF group: Albumin in serum: spectrophotometrically: 39.7 x 4.4 gn* turbidimetrically: 41.3 x 6.2 g/1 Albumin in CSF (ohly turbidimetrically): 219.5 x 52.3 mg/1** Free radicals in serum: 1.92 x O.1S mg Fe2+** **p<0.01,*p<0.5 The Wilcoxon test was used for statistical evaluation of obtained values. Discussion: The values of serum albumin, measured by spectrophotometry, are statistically different in the two studied groups. The same result was found in tase of albumin in CSF, but the concentration of albumin in CSF of patients with a disorder of the BBB was aproximatelly twice higher than in the group of probands GF. We suppose tkat this flnding cannot be explained by the passive penetration of albumin trough the damaged BBB ohly. Based on our results we assume tkat the high concentration of albumin in CSF in the GP group is caused by the necessity to protect the brain area against the serum FR attack. The expected decrease of the amount of functional thiol groups in albumin molecules is probably covered by the proces of regeneration of albumin molecules by a reaction with ascorbic acid. Conclusion: The condition of patients, suffering from damage of BBB function, is characterized by extreme elevation of albumin concentration in CSF which corresponds to the high content of FR in their serum samples. Albumin protect the brain area against the FR attack and its Scavanger ability is regenerated by action of vitamin C.

        Key words: CSF, albumin, free radicals, brain blond barrier