Urocortin 1 modulates the neurohumoral response to acute nitroprusside-induced hypotension in sheep.
In addition to haemodynamic actions, Ucn1 (urocortin 1) has been reported to affect a number of hormonal systems; however, it remains unclear whether Ucn1 modulates circulating hormones under physiological conditions. Accordingly, in the present study, we have examined the effects of Ucn1 on haemodynamics, hormones and renal indices in normal conscious sheep subjected to a nitroprusside-induced hypotensive stimulus designed to alter hormonal levels within the physiological range. Ucn1 administration did not alter the haemodynamic response to nitroprusside-induced hypotension. However, compared with the rise observed on the control day, plasma ANP (atrial natriuretic peptide; P=0.043), BNP (brain natriuretic peptide; P=0.038) and endothelin-1 (P=0.011) levels were reduced following Ucn1 administration. Associated with this significant reduction in natriuretic peptides, the increase in urinary sodium output associated with rising pressures post-nitroprusside was abolished following Ucn1 administration (P=0.048). Ucn1 had no significant effect on the response of hormones of the renin-angiotensin-aldosterone system or the hypothalamo-pituitary-adrenal axis. In conclusion, Ucn1, administered at physiologically relevant levels during nitroprusside-induced hypotension, attenuates the secretion/release of endothelin-1 and the cardiac natriuretic peptides ANP and BNP. Suppression of ANP and BNP probably led to an attenuated natriuretic response to recovery from acute hypotension. The threshold for the action of Ucn1 on the natriuretic peptides and endothelin-1 appears to be below that of other actions of Ucn1.
Charles
Christopher J
CJ
Christchurch Cardioendocrine Research Group, Christchurch School of Medicine and Health Sciences, PO Box 4345, Christchurch, New Zealand. chris.charles@chmeds.ac.nz
Rademaker
Miriam T
MT
Richards
A Mark
AM
D000450:Aldosterone / Q000378:metabolism; D000804:Angiotensin II / Q000378:metabolism; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology*; D009320:Atrial Natriuretic Factor / Q000378:metabolism; D001794:Blood Pressure / Q000187:drug effects; D002302:Cardiac Output; D003346:Corticotropin-Releasing Hormone / Q000494:pharmacology*; D006152:Cyclic GMP / Q000378:metabolism; D006339:Heart Rate / Q000187:drug effects; D007022:Hypotension / Q000378:metabolism / Q000503:physiopathology*; D020097:Natriuretic Peptide, Brain / Q000378:metabolism; D009599:Nitroprusside / Q000633:toxicity; D012756:Sheep; D054832:Urocortins
D000959:Antihypertensive Agents; D054832:Urocortins; D000804:Angiotensin II; D020097:Natriuretic Peptide, Brain; D009599:Nitroprusside; D000450:Aldosterone; D009320:Atrial Natriuretic Factor; D003346:Corticotropin-Releasing Hormone; D006152:Cyclic GMP