It’s known that perivascular adipose tissue(PVAT)has an anticontractile effect maybe mediated by adiponectin, a physiological modulator of local vascular tone with mechanism still unknown. The PVAT function is lost in obese patients with the development of adipocyte hypertrophy, hypoxia, inflammation and oxidative stress(Circulation 2009; 119(12):1661–1670).The aim of the study was to investigate functional responses of small mesenteric arteries in a animal model of genetic obesity.

Materials and Methods: we investigated 8 obese mice(B6.V-Lep ob/OlaHsd, ob/ob) and8control lean mice (CLM).Mesenteric small resistance arteries(internal diameter about 200 μm) were dissected and mounted on a wire myograph. A concentration-response curve to norepinephrine(NE, from 10⁻⁹ to 10⁻⁵ Mol/l) was evaluated in vessels with intact prerivascular fat tissue(WF) and in vessels in which perivascular fat tissue was removed(NoF) in basal conditions and during vascular hypoxia (30’,95%N₂/5%CO₂).Concentration response to NE was repeated in the presence of iberiotoxin(100 nm/L for 30’),a selective blocker of calcium-dependent potassium channels (BK_CA),that have been previously suggested to be involved in vascular tone regulation.

Results: are summarized in the figure(active media stress:KPa).The presence of PVAT reduced the contractile response to NE in both ob/ob(ANOVA p=0.002 vs. noF)and CLM(ANOVA p= 0.001 vs. NoF),however, the effect was reduced in ob/ob compared with CLM. The anticontractile effect of PVAT completely disappeard with iberiotoxin preincubation(Maximum contraction to NE.ob/ob:WF:176±47,68,NoF:218±66,02^*,WF+iberiotoxin:289±98,06^*;CLM:WF:118±53,92,NoF:245±51.8^*,WF+iberiotoxin:211±31^*;^*p<0.05 at least vs. WF) In conclusion, the anticontractile effect of perivascular fat is partially maintained in an animal model of genetic obesity. This effect may be related to the activity of BK_CA channels, since it is blocked by iberiotoxin, a scorpion toxin that inhibits calcium-dependent potassium channels