Effects of acute hypertension on the extravasation of macromolecule in the temporal bone--the possible involvement of the blood-inner ear barrier.

In guinea pigs the radioactivity in the vascular beds was washed out by a cardiac perfusion of saline 15 min after the injection of 50 microCi of radioiodinated human serum albumin (RISA). The brain and temporal bones were dissected and a blood sample was obtained. To examine the degree of extravasation of RISA, the extravascular radioactivity in the tissues was measured and expressed as a ratio to that of the blood. Intravenous injection of amphetamine sulfate increased the extravasation in the brain and the temporal bone of the rat but did not increase it in either tissue of the guinea pig. It was proposed that this was because amphetamine did not cause the blood pressure of the guinea pig to reach the "critical level" which would cause the opening of the blood-tissue barrier. In the rat the degrees of extravasation in both the brain and the temporal bone paralleled the maximal mean arterial pressure caused by amphetamine. It is proposed on the basis of these data that there may exist a blood-inner ear barrier and that this barrier has the same characteristics as the blood-brain barrier.