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Retinal histamine synthesis is increased in experimental diabetes
W J Carroll1, T M Hollis, T W Gardner
1Department of Biology, Pennsylvania State University, University Park 16802.
Investigative Ophthalmology & Visual Science
|August 1, 1988
Summary
Diabetic retinopathy involves increased retinal histamine synthesis, mediated by histidine decarboxylase. Insulin and alpha-hydrazinohistidine treatments normalize this synthesis, suggesting a new therapeutic target for diabetic eye disease.
Area of Science:
- Biochemistry
- Ophthalmology
- Metabolic research
Background:
- Diabetes mellitus is associated with microvascular complications, including diabetic retinopathy.
- Retinal vascular permeability is a hallmark of diabetic retinopathy.
- Histamine plays a role in vascular permeability and inflammation.
Purpose of the Study:
- To investigate de novo histamine synthesis in the retina of a diabetic rat model.
- To determine the role of retinal histidine decarboxylase (HDC) in this process.
- To evaluate the effects of insulin and HDC inhibition on retinal histamine synthesis.
Main Methods:
- Utilized streptozotocin-induced diabetes in male Sprague Dawley rats (21 days duration).
- Measured retinal histamine synthesis and histidine decarboxylase activity.
- Administered insulin and alpha-hydrazinohistidine (alpha HH), a specific HDC inhibitor, as treatments.
Main Results:
- The retina possesses an active histidine decarboxylase enzyme system.
- Streptozotocin diabetes significantly increased retinal histamine synthesis by 197%.
- Both insulin and alpha HH independently normalized the elevated retinal histamine synthesis.
Conclusions:
- Experimental diabetes leads to an increased inducible histamine pool in the retina.
- Insulin is identified as a key modulator of retinal histamine metabolism.
- This metabolic alteration may contribute to increased retinal vascular permeability in diabetic retinopathy.