The permeability of blood vessels in the guinea pig cochlea

Summary

Horseradish peroxidase (HRP) has been injected intravenously in order to study its transport across endothelia of modiolar blood vessels. Fixation was performed by vascular perfusion at timed intervals after injection of the trace (1/2, 1, 2, 3, 5, 8, 10, 15, 20, 25, 30, 45 and 60 min).

Fenestrated capillaries are found in the cochlear plexus only. In this region, diffusion of HRP into extracapillary spaces occurs already 1/2 min after the injection. It is possible to demonstrate the outflow of HRP across endothelial fenestrae.

Vesicular transport of HRP across nonfenestrated endothelia (capillaries of the spiral ganglion, cochlear nerve, spiral limbus and the spiral vessel) does not reach significant amounts in the time intervals studied. Although HRP is found in membrane bound endothelial vesicles already 1 min after its injection, its concentration in extravasal spaces never attains amounts necessary for its histochemical demonstration. Thus these endothelia represent a blood-perilymph barrier to HRP.