Change in the capillary permeability of the stria vascularis by different methods of death and fixation

The permeability of the stria vascularis to horseradish peroxidase (HRP) was examined. Ten minutes after an intravenous injection of HRP, 15 guinea pigs were killed and fixed by four different methods: cochleas fixed 3 minutes after decapitation, administration of an overdose of pentobarbital, cochleas fixed for 5 minutes before decapitation, and cochleas fixed immediately after decapitation. In the animals in group 1, HRP leakage was observed in almost all strial vessels (86%), and blood sludging and amorphous HRP reaction product in 98% of strial capillaries. In the animals in group 2, strial capillaries were observed both with noticeable HRP leakage and with no evidence of leakage. Blood sludging was associated with amorphous HRP reaction product, while no blood sludging was associated with granular HRP reaction product. In group 3 animals, only faint or no HRP reaction product was observed in the perivascular spaces. Only 3% of the capillaries had blood sludging. In the animals in group 4, blood sludging but no HRP leakage was observed in almost all capillaries (82%). It is speculated that HRP does not normally leak from the strial capillaries, although many researchers have reported to the contrary. It appears that HRP leaks from the strial capillaries only when acute anoxia or hypotension continues for a few minutes. These conditions induce blood sludging and are followed by the appearance of many marginal folds in these capillaries.