We assessed the permeability surface area products at the blood-retinal barrier and blood-brain barrier to
sucrose (molecular weight, 340) and
microperoxidase (molecular weight, 2000) following acute
hypertension induced by
metaraminol in Wistar-Kyoto rats (controls) and during chronic
hypertension in spontaneously hypertensive rats. In acute
hypertension, the permeability surface area product for
sucrose was increased at the blood-retinal barrier and at the blood-brain barrier over control values (p less than 0.02), and the vessels became leaky to
microperoxidase. In chronic
hypertension, the permeability of the blood-retinal barrier to
sucrose was increased over that in control animals (p less than 0.02), whereas the permeability of the blood-brain barrier was unaffected. Neither barrier leaked
microperoxidase. These results indicate that the blood-brain barrier and the blood-retinal barrier are similarly affected in acute
hypertension and that in chronic
hypertension, the blood-brain barrier is unaffected whereas the blood-retinal barrier is rendered more permeable to small, but not large, solutes.