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Hyperreactivity of coronary vasculature in platelet-perfused hearts from diabetic rats
Insights
Diabetic rat hearts show increased coronary vascular reactivity to platelet-produced eicosanoids like thromboxane B2 and prostaglandin F2 alpha. This heightened response contributes to impaired heart function in diabetes.
Area of Science:
- Cardiovascular Physiology
- Endocrinology
- Pharmacology
Background:
- Diabetes mellitus is associated with cardiovascular complications.
- Eicosanoids, particularly those derived from arachidonic acid (AA), play a role in regulating vascular tone.
- Platelet activation and subsequent eicosanoid production are implicated in vascular dysfunction.
Purpose of the Study:
- To investigate the coronary vascular responsiveness to platelet-produced eicosanoids in alloxan-diabetic rat hearts.
- To determine the specific roles of thromboxane B2 (TxB2) and prostaglandin F2 alpha (PGF2 alpha) in diabetic coronary vasoconstriction.
Main Methods:
- Isolated perfused heart model using control and alloxan-diabetic rats.
- Perfusion with platelets and arachidonic acid (AA) to stimulate eicosanoid production.
- Administration of cyclooxygenase inhibitor (ibuprofen) and thromboxane synthetase inhibitor (dazoxiben) to assess mediator roles.
Main Results:
- Diabetic rat hearts exhibited a twofold higher increase in coronary perfusion pressure compared to controls when perfused with platelets and AA.
- While TxB2 and PGF2 alpha production were comparable between groups, their contribution to vasoconstriction differed.
- Ibuprofen significantly inhibited pressure increases and eicosanoid production in both groups.
- Dazoxiben partially blocked pressure increases, completely inhibited TxB2, but enhanced PGF2 alpha production, suggesting increased sensitivity to constrictors.
Conclusions:
- Vascular reactivity to vasoconstrictor eicosanoids is significantly increased in the hearts of diabetic animals.
- Elevated levels of PGF2 alpha and potentially other constrictor eicosanoids contribute to enhanced vasoconstriction in diabetic hearts.
- These findings highlight a potential mechanism for impaired coronary blood flow regulation in diabetes.
Abstract:
Coronary vascular responsiveness to platelet-produced eicosanoids was examined in isolated perfused hearts of alloxan-diabetic rats. Coronary perfusion pressure was increased in isolated hearts of control and diabetic rats on perfusion with platelets and arachidonic acid (AA). However, the increase in perfusion pressure was approximately twofold higher in hearts of diabetic rats when compared with those isolated from control rats. This was associated with increased thromboxane B2 (TxB2) and prostaglandin F2 alpha (PGF2 alpha) production that was comparable in platelet-perfused hearts of control and diabetic animals. Ibuprofen, a cyclooxygenase inhibitor, blocked the increase in perfusion pressure and TxB2 and PGF2 alpha production by greater than 90% in both control and diabetic hearts perfused with platelets and AA. Dazoxiben, a thromboxane synthetase inhibitor, blocked the increase in perfusion pressure by 50%, totally inhibited TxB2 production, but increased PGF2 alpha production by 60% in both groups of platelet-perfused hearts. Increased levels of PGF2 alpha and possibly other constrictor eicosanoids (e.g., leukotriene D4) may account for the partial constriction observed in platelet-perfused hearts with dazoxiben. Results of the present study suggest that vascular reactivity to vasoconstrictor eicosanoids is increased in hearts of diabetic animals.