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[Bradykinin-inactivating enzyme is released from the ex-vivo stored liver]
F V Morais1, H M Molina, D R Borges
1Departamentos de Bioquímica e Medicina da Universidade Federal de São Paulo, Escola Paulista de Medicina.
Background:
The liver inactivates considerable amounts of bradykinin; the main liver kinin-inactivating enzyme (BIE, bradykinin inactivating endopeptidase) hydrolyses specifically the Phe5-Ser6 bond of the nonapeptide and it has been characterized as the oligoendopeptidase E.C.3.4.24.15. When orthotopic liver transplantation is performed there is a correlation between the increase of amino acid concentration in the preservation fluid (as a consequence of proteolysis) and graft dysfunction.
Aim:
Verify if BIE is released from livers stored ex vivo.
Method:
Wistar rats (180-220 g) livers were exsanguinated and after removal were preserved in Braun Collins fluid or Krebs solution at 4 degrees C. Aliquots were collected from the preservation fluid at 0, 4, 8, 24 h, for ALT, AST, LDH and BIE assays. The fluorimetric activity of BIE was assayed upon Abz-RPPGFSPFRQ-EDDnp (synthetic BK analogue) and its presence was confirmed by immunoblotting, revealed with specific antibody anti-E.C.3.4.24.15.
Results:
The release of ALT, AST, LDH and BIE is significant between 8-24 h. In the 24 h aliquots the four enzymes concentration increased in the Braun Collins fluid 8, 7, 19 and 10 respectively, and in the Krebs solution 21, 17, 27, 21 respectively, when compared to the zero time aliquot activities. The ratio ALT/LDH was always < 1.
Conclusion:
There is BIE release during ex vivo liver storage; this information may be useful as an indicator of the graft preservation condition; a decrease of the liver kinin-inactivating capability could affect the graft vascular reactivity.