The failure of indomethacin to alter ACTH-induced adrenal hyperaemia or steroidogenesis in the anaesthetized dog.

1 The response of adrenal blood flow to adrenocorticotropic hormone (ACTH) was measured with radioactive microspheres in anaesthetized, dexamethasone-treated, mongrel dog. 2 Adrenocorticotropic hormone (2 u/h i.v.) increased adrenal blood flow within 15 min and this persisted for the duration of the infusion. 3 Cortisol concentrations also rose with ACTH infusion. 4 Indomethacin (6 mg/kg i.v. followed by 1 mg/min) did not effect the adrenal response to ACTH although plasma concentrations of indomethacin (21.9 +/- 2.5 micrograms/ml) adequate to suppress prostaglandin synthesis were achieved. 5 We conclude that prostaglandins are not required for steroidogenesis or the adrenal haemodynamic response to ACTH.