Mechanism of noradrenaline potentiation by prostaglandin E2 in rat mesenteric artery.

1 Effects of prostaglandins E2 and F2 alpha (PGE2 and PGF2 alpha) on vasoconstrictor responses to noradrenaline (NA) and methoxamine in isolated mesenteric arteries of the rat were investigated. 2 PGE2 and to a lesser extent PGF2 alpha potentiated vasoconstrictor responses to NA and methoxamine. 3 Prior treatment with reserpine increased, and bretylium reduced, the extent of potentiation significantly. 4 NA vasoconstriction persisted for 1 h after Ca2+ was removed from the perfusing Krebs solution. Prostaglandin-induced potentiation was absent in Ca2+-free Krebs, but increased proportionately with increase in external Ca2+ concentration. 5 Vasoconstriction induced by high potassium, was not potentiated by PGE2. 6 It is concluded the PGE2 potentiates NA vasoconstriction by facilitating Ca2+ influx.