Coronary vascular hyperpermeability and angiotensin II

Elevations in plasma angiotensin II (Angll) are associated with evidence of vascular hyperpermeability expressed as efflux of plasma macromolecules into the perivascular and interstitial space. This exudative response is followed by a series of fibrogenic events that lead to a perivascular fibrosis of involved vessels. Mediators of hyperpermeability and fibrogenesis are unknown. In dogs receiving intravenous Angll, hemodynamic factors (i.e., arterial hypertension or coronary venoconstriction) were discounted as being responsible for the rise in cardiac lymph-to-plasma protein ratio. Accordingly, we investigated the relationship between AngII-induced coronary hyperpermeability and the release of prostaglandin E 2 (PGE 2 ) and activation of the basement membrane degrading matrix metalloproteinase, gelatinase/type IV collagenase. In dogs, cardiac lymph was monitored over the course of a 90-minute intravenous infusion of either Angll (0.2 to 0.3 μg/kg/min ; n = 8) or saline solution (n = 6). Lymph was examined at 30-minute intervals for the following : total protein (Lowry's method), albumin (sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE)), plasma fibronectin (SDS-PAGE and enzyme-linked immunosorbent assay) ; PGE 2 (radioimmunoassay) and gelatinase/type IV collagenase (zymography). In comparison with baseline we found a consistent rise in lymph flow (p = 0.02), total protein (p = 0.02), albumin, fibronectin, PGE 2 (p = 0.03), and gelatinase/type IV collagenase (p = 0.019), which began after 30 minutes of Angll infusion. Similar trends were not observed in dogs receiving saline solution alone. We therefore conclude that AngII-induced coronary vascular hyperpermeability is associated with an early release of PGE 2 and gelatinase.