Early increases in serum S100B are associated with cerebral hemorrhage in a rat model of focal cerebral ischemia

S100B is a 21-kD, Ca2+-binding protein that is mainly expressed in astroglial cells and Schwann cells in the nervous system. The S100B level in peripheral blood samples is reportedly elevated in patients with various central nervous system disorders including ischemic stroke. Since an elevated peripheral S100B level seems to be related closely to cerebral vascular damage involving a blood-brain barrier (BBB) disruption, we hypothesized that the peripheral S100B levels may increase earlier and to a greater extent after stroke onset when the cerebral blood vessels are severely damaged and spontaneous cerebral hemorrhage exists. In the present study, the relationship between an increase in the serum S100B level and cerebral hemorrhage was investigated within 24 h of stroke onset. A rat model for focal cerebral ischemia using an intraluminal filament method was utilized because cerebral hemorrhage is sometimes observed as a result of vascular damage caused by the filament. Significant increases in the serum S100B levels of rats with cerebral hemorrhage were observed from 1 h after stroke onset, compared with the levels in rats without cerebral hemorrhage. The early increases in serum S100B were not correlated with the brain infarct volumes at 3 h after stroke. These findings suggest that the serum S100B level increases earlier, reflecting the existence of cerebral hemorrhage.