Actions of prostaglandin precursors and other unsaturated fatty acids on conduction time and refractory period in the cat heart in situ.

1 The effect of arachidonic, dihomo-gamma-linolenic, linoleic, alpha-linolenic and oleic acid, given by intravenous infusion, on conduction time and functional refractory period have been studied in the cat heart in situ. 2 The prostaglandin precursors, arachidonic acid and dihomo-gamma-linolenic acid, prolonged the conduction time and the functional refractory period. Linoleic acid was also effective but to a lesser degree. alpha-Linolenic acid and oleic acid showed no or only a weak effect in thie respect. 3 Pretreatment was indomethacin diminished or abolished the actions of the three effective fatty acids but not those of prostaglandin E2. 4 The results suggest that the effects of prostaglandin prostaglandin precursors on conduction time and refractory period are responsible for their antiarrhythmic effectiveness and that these effects are attributable to their endogenous conversion into prostaglandins.