1. In the perfused rat mesenteric vascular bed, the effects of angiotensin II, cortisol and prostaglandin E2 on the vascular responses to noradrenaline or potassium chloride were studied.
2. Angiotensin II in subpressor concentrations potentiated the vasoconstrictor response to noradrenaline and potassium chloride. This effect of angiotensin II was inhibited in the presence of indomethacin and prostaglandin E2.
3. Cortisol in physiological concentrations inhibited the potentiating effect of angiotensin II.
4. Prostaglandin E2 enhanced the vasoconstrictor response to noradrenaline. This effect was not abolished by cortisol.
5. These results suggest that some actions of angiotensin II and cortisol in vivo are mediated by the regulation of prostaglandin synthesis or release.