Cc. Canver et al., Neurogenic vasoreactivity of human internal thoracic artery is unaffected by endothelial cell integrity, J CARD SURG, 41(4), 2000, pp. 529-532
Background The role of interval thoracic artery (ITA) nervous supply has no
t been previously considered as a potential factor influencing excellent lo
ng-term patency of an ITA graft. To define the interaction between the prim
ary afferent neurons and endothelial cells of ITA, we investigated the effe
cts of acute capsaicin administration in vitro on the isometric tension of
human ITAs.
Methods. Vessels were obtained from patients undergoing coronary bypass or
from multi-organ transplant donors. Thirty-three ITA segments (5 mm wide) w
ere suspended as rings between two stainless-steel stirrups in water-jacket
ed (37 degrees C) tissue baths. The tissue baths contained 10 ml physiologi
cal salt solution (PSS) of the following composition (mM/L): NaCl 119, KCl
4.7, NaH2PO4 1.0, MgCl2 0.5, CaCl2 2.5, NaHCO3 25, and glucose 11, aerated
continuously with 95% O-2 and 5% CO2. Peptidase inhibitors, phosphoramidon
(1 mu M) and captopril (1 mu M), were added to PSS to decrease peptide degr
adation. Mechanical responses were measured isometrically and recorded on a
polygraph via isometric force transducers, Vessels were preconstricted wit
h submaximal concentrations of norepinephrine, After the tension had stabil
ized, capsaicin was added cumulatively to the tissue bath. The viability of
ITA was verified by its responses to endothelial-dependent (acetylcholine,
1 mu M) (n=20) and endothelial-independent (sodium nitroprusside, 10 mu M)
(n=13) vasodilators.
Results. The exposure of capsaicin (3 mu M) to human ITA produced varied ef
fects on ITA irrespective of its endothelium, Capsaicin induced contraction
of the ITA smooth muscle in 13 endothelium-intact ITA segments while it pr
oduced vasoconstriction in 9 endothelium-denuded ITAs (p=0.6437). In respon
se to capsaicin, relaxation of ITA smooth muscle was observed in 7 ITA ring
s with endothelium, while vasodilation was present in 4 ITA segments withou
t endothelium (p=0.4099).
Conclusions, Capsaicin-sensitive neurons encircling human ITA produce a neu
rogenic vasoreactive response independent of ITA endothelial cell integrity
.