Increased conversion of arachidonic acid to vasodilator prostanoids in spontaneously hypertensive rats

1. Vasodepressor responses to intravenous injection of prostacyclin, arachidonic acid, and nitroprusside were examined in anaesthetized, spontaneously hypertensive rats (SHR) of the Okamoto strain, and in their normotensive Wistar-Kyoto (WKY) controls. 2. Depressor responses to prostacyclin and nitroprusside did not differ significantly between the two strains. 3. The vasodepressor effects of arachidonic acid were greater and much more prolonged in SHR than in WKY. In rats treated with indomethacin (2 mg/kg) arachidonic acid induced only transient depressor responses which did not differ significantly between these strains. 4. It is concluded that SHR do not differ from WKY in their sensitivity to prostacyclin but they have enhanced ability to transform exogenous arachidonic acid into vasodilator prostanoids.