INVESTIGADORES
JOO TURONI Claudio Martin
congresos y reuniones científicas
Título:
Impacto de la Hipertensión en la reactividad del bypass de arteria mamaria. Rol del óxido nítrico extraendotelial
Autor/es:
MARAÑON RODRIGO; JOO TURONI CLAUDIO; PROTO VÍCTOR; COVIELLO ALFREDO; PERAL DE BRUNO MARIA
Lugar:
Buenos Aires
Reunión:
Congreso; XIII Congreso Argentino de HTA; 2006
Institución organizadora:
Sociedad Argentina de HTa
Resumen:
Internal mammary artery (IMA) used in bypass coronary surgery remains functional
for longer periods than other grafts. Objective. To compare in IMA grafts from
hypertensive (HT) and normotensive (NT) patients the presence of endothelium and its
functionality, the degree of vascular compliance and basal tone, the reactivity to exogenous
vasoconstrictors, and the role of stretching in NO-release. Methods. Segments of
IMA were connected to a isometric force transducer. Nitrites were measured by Griess
reaction by absorbance at 540 nm. Endothelial integrity was evaluated by histological
(H&E) and immunohistochemistry examinations (monoclonal CD34 antibodies). For
immunohistochemistry visualization of nNOS, slides were incubated with rabbit antibody
anti-nNOS. Results. An endothelial dysfunction associated with hypertension was
found. IMA rings from HT had an impaired response to passive stretching, resulting in a
decreased relaxation. All IMA grafts had an increased basal tone demonstrated by relaxation
to SNP; however, a lesser response was found in HT. Interestingly, it was demonstrated
that NO release was present in IMA grafts, despite an endothelial dysfunction,
and that stretching increased this NO release. This effect was inhibited by Ca2+-free
media, L-NAME and a specific neuronal NO synthase (nNOS) inhibitor. Furthermore,
in smooth muscle cells from stretched IMA, the presence of nNOS by immunohistochemistry
was found. Conclusion. We show the impact of hypertension in IMA grafts,
producing increased endothelial dysfunction, reduced vascular compliance, increased
basal tone, and impaired responsiveness to exogenous vasoconstrictors and NO release.
A specific role of the stretching in extraendothelial NO release was demonstrated,
which may have an important role in the outcome of IMA grafts due to the protective
actions of NO. Keywords. IMA grafts, hypertension, endothelial dysfunction, vascular
reactivity, extraendothelial nitric oxide synthase.