The relationship between functional vasodilatation in adipose tissue and prostaglandin.

1. Earlier it had been found that during fat mobilization there was an increased blood flow in the adipose tissue and the tissue contained a vasodilator substance.2. Extract of an activated fat pad contained 3 to 25 times as much activity as the contralateral resting fat pad.3. The following findings suggest that the vasodilator substance is prostagladin E(2):(a) It caused contractions of the guinea-pig ileum which were not reduced by mepyramine, but were reduced by atropine.(b) It caused a prolonged vasodilator response when injected closearterially to the epigastric fat pad.(c) It was eluted from a silicic acid column by a solvent system which is known to elute prostaglandins of the E series but not those of the F series.(d) Its indices of discrimination were similar to those of prostaglandin E's when assayed on three different pharmacological preparations.(e) On thin-layer chromatography it behaved more like prostaglandin E(2) than E(1).4. Neither prostaglandin E(1) nor prostaglandin E(2) inhibited the release of free fatty acids from the rabbit epigastric fat pad by ACTH(1-24).5. It seems likely that prostaglandin E(2) is responsible for the vasodilatation accompanying fat mobilization from adipose tissue.