Vascular Actions of Frusemide and Bumetanide on the Rat Superior Mesenteric Vascular Bed: Interactions with Prostaglandins

1. The addition of frusemide or bumetanide to perfusion fluid inhibited the response of the isolated mesenteric vascular bed to noradrenaline.

2. Addition of prostaglandin E₂ to the perfusion fluid completely restored the response to noradrenaline.

3. Inhibition of prostaglandin secretion by indomethacin with restoration of responses to noradrenaline by the addition of exogenous prostaglandin E₂ prevented the inhibitory effect of frusemide or bumetanide on responses to noradrenaline.

4. The inhibitory effects of diuretics on responsiveness to noradrenaline is mediated by blockade of endogenous prostaglandin synthesis.