Diffuse cytoplasmic staining of retinal capillary endothelium

Area of Science:

• Ophthalmology
• Cell Biology
• Histology

Background:

• The blood-retinal barrier (BRB) is crucial for retinal function.
• Hemeprotein tracers are often used to study BRB permeability.
• Non-specific binding of tracers can complicate interpretation.

Purpose of the Study:

• To investigate the distribution of hemeprotein tracers in rat retinal capillaries.
• To determine if tracers cause non-specific staining in endothelial cells.
• To assess the impact of tracer distribution on BRB integrity.

Main Methods:

• Electron microscopic cytochemistry was used to visualize tracer distribution.
• Wistar-Furth rats were injected or perfused with various hemeprotein tracers.
• 3,3'-diaminobenzidine was used as the incubation substrate.

Main Results:

• Horseradish peroxidase (HRP) and lactoperoxidase (LP) caused diffuse cytoplasmic staining in endothelial cells and occasional pericyte staining.
• Microperoxidase, catalase, and hemoglobin did not induce diffuse staining.
• Staining occurred with different HRP types and concentrations, without compromising the blood-retinal barrier.

Conclusions:

• HRP and LP can lead to non-specific, diffuse staining of retinal capillary endothelial cells.
• The presence of this non-specific staining necessitates cautious interpretation of BRB studies using these tracers.
• Findings highlight potential artifacts in research relying on HRP and LP for BRB permeability assessment.