Cardiovascular and neurohormonal effects of intravenous adrenomedullin in conscious rabbits. Fukuhara, Masayo, Takuya Tsuchihashi, Isao Abe, Masatoshi Fujishima. Second Department of Internal Medicine, Faculty of Medicine, Kyushu University, Fukuoka, Japan
APStracts 2:0225R, 1995.
Adrenomedullin is a vasodilative peptide and shows slight homology with calcitonin gene-related peptide. In the present study, we investigated the effects of adrenomedullin on cardiovascular and neurohormonal responses in 13 conscious rabbits. The animals were chronically instrumented bipolar electrodes on the left renal sympathetic nerve. The intravenous administration of human adrenomedullin (10, 100, 1000, 3000 pmol/kg, n=6) caused a dose -dependent reduction in mean arterial pressure (0+/-2, -1+/-2, -19+/ -2, -29+/-4 mmHg, respectively) concomitantly with increases in heart rate, renal sympathetic nerve activity, plasma renin activity and plasma norepinephrine. The significant reduction in mean arterial pressure induced by 1000 pmol/kg of adrenomedullin occurred within 1 minute after injection and lasted for 15 minutes (n=7). In contrast, the significant increases in heart rate and renal sympathetic nerve activity lasted for more than 50 minutes. When mean arterial pressure was decreased by 15 mmHg by adrenomedullin, the increases in heart rate and renal sympathetic nerve activity were 53+/-8 beats/min and 78+/-13%, respectively, which were significantly smaller than those induced by the intravenous injection of sodium nitroprusside (102+/ -14 beats/min and 155+/-34%, respectively). These results suggest that intravenous adrenomedullin exerts a hypotensive action which is associated with the attenuated reflex-mediated sympathetic activation. 

Received 7 March 1995; accepted in final form 27 July 1995.
APS Manuscript Number R149-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 14 August 1995.