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PMN accumulation in aqueous humor and iris-ciliary body during intraocular inflammation
Abstract:
The accumulation of polymorphonuclear leukocytes (PMNs) was determined in the aqueous humor and iris-ciliary body following an intravitreal injection of endotoxin in the albino rabbit. PMN accumulation in the iris-ciliary body was quantified by measuring myeloperoxidase (MPO) activity in homogenates of this tissue. Leukocyte appearance in the aqueous humor was determined by counting the number of PMNs in diluted aspirates of aqueous humor and also by measuring MPO activity in the same aspirates. Twenty-four hours following an intravitreal injection of endotoxin, there was marked vasodilatation in the iris, breakdown of the blood-aqueous barrier, and infiltration of PMNs into the aqueous humor. There was, however, no correlation between MPO activity in the iris-ciliary body and the number of PMNs or the MPO activity in the aqueous humor. Furthermore, the number of PMNs in the aqueous humor did not increase with increasing amounts of intravitreally injected endotoxin, whereas MPO activity in the iris-ciliary body increased in a dose-dependent manner. The results of this study suggest that quantification of leukocytes in the aqueous humor does not represent a meaningful index of intraocular inflammation.
Insights
Measuring polymorphonuclear leukocytes (PMNs) in aqueous humor is not a reliable indicator of intraocular inflammation. Myeloperoxidase (MPO) activity in the iris-ciliary body better reflects endotoxin-induced inflammation in rabbits.
Area of Science:
- Ophthalmology
- Immunology
- Veterinary Medicine
Background:
- Intraocular inflammation is a significant concern in ophthalmology.
- Polymorphonuclear leukocytes (PMNs) are key inflammatory cells.
- Accurate assessment of intraocular inflammation is crucial for effective treatment.
Purpose of the Study:
- To evaluate the correlation between PMN accumulation in the aqueous humor and iris-ciliary body.
- To determine the reliability of aqueous humor PMN counts and myeloperoxidase (MPO) activity as indicators of intraocular inflammation following endotoxin injection.
Main Methods:
- Intravitreal injection of endotoxin in albino rabbits.
- Quantification of PMN accumulation in the iris-ciliary body via MPO activity.
- Assessment of leukocytes in aqueous humor by direct cell counting and MPO activity measurement.
Main Results:
- Endotoxin induced vasodilatation, blood-aqueous barrier breakdown, and PMN infiltration into the aqueous humor.
- No correlation was found between MPO activity in the iris-ciliary body and PMN counts or MPO activity in the aqueous humor.
- Iris-ciliary body MPO activity showed a dose-dependent increase with endotoxin, while aqueous humor PMN counts did not.
Conclusions:
- Quantifying leukocytes in the aqueous humor is not a meaningful index of intraocular inflammation.
- MPO activity in the iris-ciliary body is a more reliable measure of endotoxin-induced intraocular inflammation.
- Further research may be needed to establish optimal biomarkers for intraocular inflammation.