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Cytoplasmic contractile apparatus in aortic endothelial cells of hypertensive rats
Abstract:
Hypertension was produced in male Wistar rats (150 gm. body weight) by complete ligature of the aorta between the renal arteries. Electron microscopic examination revealed that 1 week later the amount of cytoplasmic microfilaments in the endothelial cells of the aortic segment above the coarctation (mean blood pressure 160 mm. Hg) was strikingly increased as compared with normal animals. The endothelial cells in the segment below the coarctation (mean blood pressure 25 mm. Hg) contained few filaments and were similar to the cells in the aortic endothelium in controls (mean blood pressure 105 mm. Hg). Microfilaments measured 40 to 70 angstrom in diameter and were mostly located close to the endothelial clefts, where they formed longitudinal bundles or a network. The bundles of microfilaments contained electron-dense areas similar to the "attachment sites" of the underlying smooth muscle. By using en face preparations of aortic endothelial cells treated with antiactin autoantibodies (AAA) followed by anti-human IgG, it was seen that in hypertensive animals the cells above the ligature were intensely fluorescent when compared with those of the aortic portion below the ligature or those of the controls. The fluorescence was abolished after incubation of the AAA sera with thrombosthenin A. The correlation between electron microscopic and immunologic findings suggests that the microfilaments present in the endothelial cells of hypertensive animals are composed, at least in part, of actin. Endothelial cells so modified may play a role in permeability or may be related to other phenomena such as electrotonic coupling and synchronized contraction of aortic cells during hypertension.
Insights
Hypertension significantly increases cytoplasmic microfilaments in rat aortic endothelial cells, suggesting actin involvement. These changes may impact vascular function during high blood pressure.
Area of Science:
- Vascular Biology
- Cellular Physiology
- Hypertension Research
Background:
- Hypertension is a major cardiovascular risk factor.
- Endothelial cell structure and function are critical in maintaining vascular homeostasis.
- Changes in endothelial cell cytoskeleton are implicated in vascular disease.
Purpose of the Study:
- To investigate alterations in endothelial cell microfilaments during experimental hypertension.
- To determine the composition of these microfilaments.
- To explore their potential role in hypertension-related vascular changes.
Main Methods:
- Induction of hypertension in Wistar rats via aortic coarctation.
- Electron microscopy of aortic endothelial cells.
- Immunofluorescence using antiactin autoantibodies (AAA).
Main Results:
- Hypertensive aortic segments showed a marked increase in endothelial cytoplasmic microfilaments compared to controls.
- Microfilaments were localized near endothelial clefts, forming bundles and networks.
- Immunofluorescence revealed intense actin labeling in hypertensive endothelial cells, suggesting actin presence.
- Fluorescence was specifically reduced upon incubation with thrombosthenin A.
Conclusions:
- The study provides evidence that actin-rich microfilaments accumulate in endothelial cells of hypertensive rats.
- These cytoskeletal modifications may contribute to altered endothelial permeability and cell-cell communication in hypertension.
- Endothelial actin dynamics are a potential target for understanding and managing hypertension.