HIGH INHIBITORY ACTIVITY ON PROTEASES IN A REPTILE PLASMA (BOTHROPS-JARARACA SNAKE) IMPAIRS ITS INTRINSIC FIBRINOLYTIC-LIKE MECHANISM

1. A mammal-like fibrinolytic system was investigated in the blood of male and female poisonous snakes Bothropsjararaca (Bj). 2. Conventiona l and alternative methodologies were used to study this mechanism in p lasma and euglobulin fraction (EUF) since it was previously reported t hat classes Aves and Reptilia did not have this system. 3. EUFs from m ale and female snakes showed activity on fibrin-agarose plates when di luted plasma (1:20) was precipitated at pH 5.9, No activity was seen a t pH 5.5, and very little or occasional at pH 5.7. 4. A 79 KDa activat or of fibrinolysis was detected in EUF of both sexes after SDS-PAGE an d zymography independently of the pH of precipitation. 5. Activity of EUF measured on conventional human fibrin plates was variable and incr eased by overnight standing at 4 degrees C and/or addition of flufenam ates. 6. The difference in behaviour described in items 3 and 5 may be due to a sieving effect in the fibrin-agarose plates which by separat ing activators and inhibitors allows the expression of fibrinolytic ac tivity, The same principle could explain the results after SDS-PAGE an d zymography. 7. Bj plasma showed high inhibitory activity on fibrin l ysis by the proteases trypsin and plasmin and, moderate on the same ac tivity by plasminogen activators, urokinase (UK) and tissue activator (t-PA), Reverse zymography of plasma on fibrin agarose plates showed a n inhibition area in the range of 45 to 69 KDa as compared to rabbit P AI-1 in a single band of 42 KDa. 8. Bj plasma was more inhibitory to U K when compared to human, bovine and rabbit plasma on fibrinagarose pl ates, Bj female plasma was more inhibitory than male. 9. Euglobulin cl ot lysis time (ECLT) for Bj EUFs was very prolongated even in high dil ution (1:30) when compared to the human system, Correction of the ioni c strength in higher dilutions did not improve the ECLT of Bj EUFs, wh ich was decreased only by further addition of UK (30 IU) to EUF from d ilution 1:60. 10. It is suggested that a mammal-like fibrinolytic syst em operates on Bj snake plasma, However, a different balance of activa tor-inhibitor levels seems to hinder the detection of the lytic activi ty.