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Thrombin contracts isolated bovine retinal small arteries in vitro
1Department of Pharmacology, Aarhus University, Denmark.
Investigative Ophthalmology & Visual Science
|November 1, 1990
Summary
Thrombin causes bovine retinal arteries to contract in a dose-dependent manner, requiring its catalytic activity. This effect is not mediated by alpha-adrenergic receptors or prostaglandins.
Area of Science:
- Vascular Pharmacology
- Ocular Physiology
Background:
- Thrombin is a key enzyme in hemostasis.
- Its role in regulating retinal microvasculature is not fully understood.
Purpose of the Study:
- To investigate the in vitro effects of thrombin on bovine retinal small arteries.
- To characterize the concentration-dependent contractile responses and underlying mechanisms.
Main Methods:
- Isolated bovine retinal artery rings were used in an organ bath setup.
- Cumulative concentrations of thrombin were added to assess contractile responses.
- Experiments included testing inactivated thrombin, phenoxybenzamine, indomethacin, and methylene blue.
Main Results:
- Thrombin induced variable, concentration-dependent contractions in retinal arteries.
- Contractions were slow, sustained, and dependent on thrombin's catalytic activity.
- Responses were not affected by phenoxybenzamine or indomethacin, but potentiated by methylene blue in larger arteries.
Conclusions:
- Thrombin exerts a direct contractile effect on bovine retinal arteries.
- The mechanism involves thrombin's catalytic activity, independent of alpha-adrenergic or cyclooxygenase pathways.
- Potential modulation by nitric oxide pathways warrants further investigation.