Relationship between blood flow and blood-brain barrier permeability of sodium and albumin in focal ischaemia of rats: a triple tracer autoradiographic study.

Local cerebral blood flow, the permeability of the blood-brain barrier to sodium and serum albumin, and the content of electrolytes were investigated in rats before and at 4 h and 24 h following permanent occlusion of the middle cerebral artery (MCA). Measurements were carried out by triple tracer autoradiography, using 131I-iodoantipyrin, 22NaCl and 125I-iodinated bovine serum albumin, respectively. Regional sodium and albumin transfer coefficients were calculated by multiple time point analysis, and correlated with the corresponding flow and tissue electrolyte values. In sham operated controls regional sodium and albumin transfer coefficients ranged between 2.16-2.30 x 10(-3) and 0.22-0.48 x 10(-3) ml/min per g, respectively. Four hours after MCA occlusion sodium and albumin transfer coefficients were unchanged although tissue sodium content was already increased. After 24 h the sodium-but not albumin-transfer coefficient increased 2-3 fold but the rise in tissue sodium content was slower than after 4 h. At both ischaemia times the unidirectional sodium influx was substantially higher than the actual changes of tissue sodium content. The development of stroke oedema is, therefore, not limited by the alterations of barrier permeability.