5,6-DiHET lactone is a lactonized form of 5,6-EET and 5,6-DiHET. In solution, 5(6)-EET degrades into 5(6)-DiHET and 5(6)-δ-lactone, which can be converted to 5(6)-DiHET and quantified by GC-MS. 5,6-DiHET potently induces vasodilation of isolated canine coronary arterioles, with 41 and 100% inhibition occurring at 0.01 and 100 pM, respectively. It also induces vasodilation in isolated human microvessels and increases intracellular calcium levels in a dose-dependent manner, an effect that can be blocked by the nitric oxide scavenger L-NAME .