Perivascular adipose on relaxation of internal thoracic artery with surgical implications: Better antispastic effect of pedicle than skeletal grafts.

Abstract

The internal thoracic artery (ITA) is the first choice for coronary artery bypass grafting. However, the effect of perivascular adipose tissue (PVAT) on its vasomotor regulation has not been fully studied. PVAT may secrete adipokines, such as adiponectin, which plays a role in vasodilation, thus potentially enhancing graft function and antispasmodic ability. Human ITA rings were obtained from patients undergoing coronary artery bypass grafting and mounted in a wire myograph. Rings were precontracted with U46619 (10^-7 M), followed by cumulative application of synthetic agonist of adiponectin receptors (AdipoRon) (10^-8 to 10^-4 M) or calcium ionophore (A23187) (10^-9 to 10^-4 M). Groups included endothelium-intact or denuded rings, with or without PVAT, and with or without the nitric oxide synthase inhibitor Nω-nitro-L-arginine. PVAT samples were also incubated with AdipoRon or A23187 for 24 hours, and adiponectin secretion was measured by enzyme-linked immunosorbent assay. Both AdipoRon and A23187 induced concentration-dependent vasorelaxation. PVAT significantly enhanced vasorelaxation compared with PVAT-removed rings (P < .001). Under nitric oxide synthase inhibition, PVAT presence still augmented relaxation (P < .001), and in PVAT presence rings lacking both endothelium and nitric oxide, partial A23187-induced relaxation was preserved (P < .001). Enzyme-linked immunosorbent assay showed that AdipoRon had no significant effect (P = .14), whereas A23187 significantly increased adiponectin secretion (P < .001), indicating a calcium-dependent mechanism of adiponectin release. PVAT exerts potent vasodilatory effects on human ITA, even in the absence of nitric oxide and endothelium. These findings support the physiological benefit of preserving PVAT, as in pedicled ITA grafts, which may enhance graft relaxation and reduce or ameliorate vasospasm during coronary artery bypass grafting.