Radial artery frequently develops
spasm and requires
vasodilator therapy during
coronary artery bypass graft surgery (CABG).
Levosimendan was recently shown to oppose 5-hydroxytryptamine-induced contraction of radial artery (RA) grafts. The aim of the present study was to explore whether
levosimendan retains its vasodilatory capacity following in vitro pre-incubation of RA segments with the inodilator. A possible cumulative effect of the
drug in human platelets was also studied. Human isolated RA segments were pre-incubated in 0.16 μmol/L
levosimendan containing
solution or in
0.9% NaCl, Bretschneider, 5%
albumin and a 5% human
serum protein solution (Biseko) as controls for 45 min. Contractions were induced by three consecutive administrations of
5-hydroxytryptamine (0.31 μM) 45, 90 and 120 min. after exchanging the pre-incubation solutions with
Krebs-Henseleit solution, uniformly. Receptor-independent contractions (KCl, 80 mmol/L), endothelium-dependent (
acetylcholine, 1 μmol/L) and independent relaxations (
papaverine, 100 μmol/L) were also investigated. Washed human platelets were pre-incubated with
levosimendan (0.06 μmol/L) for 2 or 15 min. and aggregated with
thrombin (0.1 IU/mL). Contractions of RA grafts induced by
5-hydroxytryptamine were significantly smaller 45 min. and 90 min. after the replacement of
levosimendan with
Krebs-Henseleit solution. Biseko
solution also decreased the contraction of the graft at 45 min. Contractions did not change in time following the pre-incubations of radial arteries with
0.9% NaCl, Bretschneider and 5%
albumin solutions. The grafts remained intact as assessed by their maximum contractions and endothelium-dependent and endothelium-independent relaxations at the end of the investigations. Platelets revealed larger anti-aggregatory effect to
levosimendan following the enhancement of the incubation time. Results indicate that the
antispasmodic and anti-aggregatory effects of
levosimendan cumulate in the vascular tissue and in platelets. The storage of RA with the inodilator before implantation may help to prevent the intraoperative
spasm of the graft and also thrombotic occlusion during CABG surgery.