Extravascular plasminogen activator and inhibitor activities detected at the site of a chronic mycobacterial-induced inflammation.
Levels of extravascular tissue plasminogen activator activity (PA) and those of inhibitors of PA and of urokinase (UK) present within the anterior chamber of normal and inflamed feline eyes were assessed with the use of a direct PA assay of microsamples of aqueous humor. Purposes of the study were, first, to confirm prior indirect evidence that this extravascular space normally contains higher levels of uninhibited PA, but lower levels of inhibitor activity, than does plasma and, second, to determine patterns of change in these activities under in vivo conditions imposed by a chronic mycobacterial-induced uveitis (CMIU) disease model. The PA assay utilized a 125I-plasminogen substrate whose cleavage by PA contained in samples was both visualized during gel electrophoreis, and quantified by gamma counting. The results provided the first direct evidence that the higher fibrinolytic activity previously observed in normal aqueous in comparison with plasma is in fact associated with higher levels of available (uninhibited) PA (P less than 0.01) The data also indicated that normal aqueous contains a much higher level of PA inhibitor activity than previously suspected--roughly 40 times more than available PA levels. These normal values for PA and inhibitors occupied a relatively narrow, threefold range, in contrast to the wide scattering of individual values that appeared during 18-20 weeks of the chronic inflammation disease model. Despite this, however, the general pattern of observation for all individual eyes during CMIU was a significant increase in levels of both PA and inhibitors. The net effect of CMIU was thus to cause the 1:40 ratio noted above to be tilted more strongly in favor of inhibitor activity, ie, up to 1:80. Increases in local vasopermeability in this disease model were believed contributory to this change. However, local generations of PA and APA in vivo by inflammatory cells, especially monocyte-macrophages, must also be considered. Assays for UK inhibitor showed levels of activity and directions of change that closely followed those of PA inhibitor, which suggests the possibility that they may be identical. It is surmised that the above patterns, along with results of our prior studies, indicate an apparent need for a multistep, strict inhibitory control of plasmin generation and proteolysis in vivo within normal extravascular spaces such as the anterior chamber.(ABSTRACT TRUNCATED AT 400 WORDS)
O'Rourke, J; Wang, WP; Donnelly, L; Wang, E; Kreutzer, DL
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