Relationship between cerebrospinal and peripheral S100B levels after focal cerebral ischemia in rats.

S100B is a 21-kDa, Ca(2+)-binding protein that is expressed in the central nervous system. Although the peripheral S100B level is significantly correlated with stroke outcome, the mechanisms responsible for increase in the peripheral S100B level have not been precisely investigated in animal ischemic stroke models. To justify the use of peripheral S100B as a common biomarker between stroke patients and animal models, the mechanisms responsible for increases in the peripheral S100B level after focal cerebral ischemia should be clarified. In the present study, we investigated correlations between the cerebrospinal and serum S100B levels to determine whether increase in peripheral S100B properly reflect the conditions inside the central nervous system. From each rat, cerebrospinal fluid and serum samples were collected at 24, 48, 72, or 120 h after the onset of photochemically induced thromboembolic stroke in rats. Our results indicated a difference in the kinetics of cerebrospinal and serum S100B. Among the four sampling points, the serum S100B levels were most strongly correlated with the cerebrospinal S100B levels at 48 h after PIT stroke onset. While the serum S100B level may be a useful biomarker of stroke in experimental or clinical studies, the timing of S100B measurements should be carefully selected to ensure that the serum S100B level properly reflects the conditions in the central nervous system.