gms | German Medical Science

Virtually all systemic blood vessels are surrounded by adipose tissue, which produces a number of biologically active substances, including adiponectin. We have previously reported that perivascular adipose tissue secretes adipocyte-derived relaxing factor (ADRF) to relax aorta and mesenteric arteries by opening of smooth muscle K+ channels in rats. The nature of ADRF and it's putative role in other species are unknown. We tested the hypothesis that periadventitial adipose tissue modulates contraction of small mesenteric arteries in mice and examined the role of adiponectin as possible candidate of ADRF. We studied mesenteric artery rings surrounded by periadventitial adipose tissue from 6-8 weeks C57BL/6 mice. The contractile response to serotonin was markedly reduced in intact vessels compared to vessels without periadventitial fat. The contractile response to depolarizing high K+ containing solutions (60 mM) was similar in vessels with and without periadventitial fat. The anti-contractile effect of periadventitial fat was abolished by inhibition of delayed-rectifier K+ (Kv) channels with 4-aminopyridine (2 mM). Blocking other K+ channels had no effect. Adiponectin inhibited serotonin-dependent contractions in a dose-dependent manner, with half-maximal effects at 5 µg/ml. Similar adiponectin plasma levels were measured in rats and mice. We suggest that visceral periadventitial adipose tissue controls mesenteric arterial tone locally by inducing vasorelaxation via Kv channel activation in vascular smooth muscle cells. Furthermore, adiponectin represents a possible candidate for ADRF.