Cardiovascular research
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Cardiovascular research · Feb 2001
Biological action of angiopoietin-2 in a fibrin matrix model of angiogenesis is associated with activation of Tie2.
The endothelial cell (EC) specific tyrosine kinase receptor, Tie2, interacts with at least two ligands, angiopoietin-1 (Ang1) and angiopoietin-2 (Ang2). Ang1 stimulates Tie2 receptor autophosphorylation, while Ang2 has been reported to inhibit Ang1-induced Tie2 receptor autophosphorylation. We studied the effects of Ang1 and Ang2 in an in vitro model of angiogenesis. ⋯ Although Ang2 was unable to induce significant Tie2 receptor phosphorylation during a 5-min exposure, a 24-h pretreatment with Ang2, followed by brief re-exposure, produced Tie2 phosphorylation in HUVEC comparable to that produced by Ang1*. These results demonstrate for the first time that Ang2 may have a direct role in stimulating Tie2 receptor signaling and inducing in vitro angiogenesis. Our findings suggest that the physiological role of Ang2 is more complex than previously recognized: acting alternately to promote or blunt Tie2 receptor signaling in endothelial cells, depending on local conditions.
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Cardiovascular research · Feb 2001
Comparative StudyGender-related differences in left ventricular chamber function.
While women have lower rates of atherosclerotic disease than men, they are more likely to suffer cardiac failure following infarction or cardiac surgery, despite typically having a greater left ventricular (LV) ejection fraction. We hypothesised that gender differences in systolic chamber function and ventriculo-vascular coupling may contribute to these clinical findings. ⋯ This study demonstrates greater systolic chamber function and lower diastolic compliance in women. Within the range of chamber dimensions seen in patients with normal LV function, a strong relationship was found between cardiac size and end-systolic elastance. While these differences were not accounted for by indexing to body size, the greater ventricular elastance in women was removed after normalising to chamber size. Despite differences in resting ventricular elastance, appropriate ventriculo-vascular coupling was maintained in both genders as the greater end-systolic elastance in women was matched by similarly elevated arterial elastance.