Atividades e expressão de peptidases em ratos tratados cronicamente com L-NAME, um inibidor da biossintese de oxido nitrico, e em ratos espontaneamente hipertensos

AUTOR(ES)

Alessandra Linardi

DATA DE PUBLICAÇÃO

2004

RESUMO

Peptidases play an important role in modulating the activity of endogenous peptides in normal and pathological situations. In this work, we investigated the activity and expression of four peptidases (aminopeptidase M - APM, dipeptidyl peptidase IV - DPP IV, metalloendopeptidase 24.15 - MEP 24.15 and neutral endopeptidase 24.11 - NEP 24.11) in rat tissues (aorta, brain, heart, kidney, liver and lung) in two models of hypertension, namely, chronic treatment with NlV-nitro-Larginine methyl ester (L-NAME), a nitric oxide (NO) synthase inhibitor (80 mg kg-1 dai1, p.o. for 4 weeks), and spontaneously hypertensive rats (SHR). Enzymatic activity was assayed fluorometrically or colorimetrically and protein expression was assessed by westem blotting. Treatment with L-NAME did not significantly alter the activities of the four peptidases in brain, heart, kidney, liver and lung (NEP was detected only in kidney and lung). In contrast, in thoracic aorta, the activity of APM was slightly but significantly reduced whereas those of DPP IV and MEP 24.15 were markedly enhanced. Immunoblotting for DPP IV and MEP 24.15 showed increased expression in aortic tissue. Neither L-NAME (1-100 J.lM)nor the NO donors sodium nitroprusside and 3-morpholinosydnonimine (1-100 J.lMeach) had any consistent effect on the activity of recombinant MEP 24.15 or renal DPP IV. Administration of the MEP 24.15/MEP 24.16 inhibitor N-[1-(R,S)-carboXy-3- phenylpropyl]-Ala-Aib-Tyr-p-aminobenzoate (JA2) in pentobartibal-anesthetized rats significantly potentiated the hypotensive response to bradykinin. In SHR, the activity of DPP IV was significantly increased in brain, whereas MEP 24.15 and NEP 24.11 activities were markedly enhanced in lung (MEP 24.15 and NEP 24.11) and kidney (NEP 24.11). In contrast, the activities of DPP IV and MEP 24.15 were markedly decreased in aortic tissue; APM was unaltered and NEP 24.11 was not detected in this tissue. Immunoblotting for DPP IV and MEP 24.15 showed decreased expression in aortic tissue and increased expression of DPP IV in the brain; there was no alteration in the expression of MEP 24.15 in the lung or of NEP 24.11 in kidney and lung. The administration of JA2 to SHR did not alter the responses to bradykinin. These results indicate that there were alterations in the activity and expression of the peptidases studied (except for APM) in both models of hypertension. However, the different patterns of afterations seen between the two models suggests that the changes were not caused by the hypertension per se, but rather were probably the result of biochemical alterations associated with each model and selective for each peptidase

ASSUNTO(S)

farmacologia oxido nitrico hipertensão

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