Regional haemodynamic effects of human and rat adrenomedullin in conscious rats.
1. Male, Long Evans rats were chronically instrumented with pulsed Doppler flow probes and intravascular catheters to permit assessment of the regional haemodynamic responses to human and rat adrenomedullin, to compare the responses to human adrenomedullin to those of human alpha-CGRP in the absence and presence of the CGRP1-receptor antagonist, human alpha-CGRP [8-37], and to determine the involvement of nitric oxide (NO)-mediated mechanisms in the responses to human adrenomedullin, relative to human alpha-CGRP. 2. Human and rat adrenomedullin (0.3, 1, and 3 nmol kg-1, i.v.) caused dose-dependent hypotension and tachycardia, accompanied by increases in renal, mesenteric and hindquarters flows and vascular conductances. At the lowest dose only, the hypotensive and mesenteric vasodilator effects of rat adrenomedullin were significantly greater than those of human adrenomedullin. 3. Human alpha-CGRP at a dose of 1 nmol kg-1 caused hypotension, tachycardia and increases in hindquarters flow and vascular conductance, but reduction in renal and mesenteric flows, and only transient vasodilatations in these vascular beds. These effects were substantially inhibited by human alpha-CGRP [8-37] (100 nmol kg-1 min-1), but those of human adrenomedullin (1 nmol kg-1) were not; indeed, the mesenteric haemodynamic effects of the latter peptide were enhanced by the CGRP1-receptor antagonist. 4. In the presence of the NO synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME, 183 nmol kg-1 min-1), there was only a slight, but significant, inhibition of the hindquarters hyperaemic vasodilator effect of human adrenomedullin, but not that of human alpha-CGRP. 5. These results indicate that the marked regional vasodilator effects of human (and rat) adrenomedullin are largely independent of NO and, in vivo, do not involve CGRP1-receptors.
Gardiner
S M
SM
Department of Physiology & Pharmacology, University of Nottingham Medical School, Queen's Medical Centre.
Kemp
P A
PA
March
J E
JE
Bennett
T
T
D053607:Adrenomedullin; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D000959:Antihypertensive Agents / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D001120:Arginine / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D015740:Calcitonin Gene-Related Peptide / Q000008:administration & dosage / Q000037:antagonists & inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D002406:Catheterization, Peripheral; D004305:Dose-Response Relationship, Drug; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects*; D006801:Humans; D006973:Hypertension / Q000188:drug therapy; D007022:Hypotension / Q000139:chemically induced; D017078:Laser-Doppler Flowmetry; D008297:Male; D019331:NG-Nitroarginine Methyl Ester; D009569:Nitric Oxide / Q000037:antagonists & inhibitors; D010446:Peptide Fragments / Q000008:administration & dosage / Q000494:pharmacology; D010455:Peptides / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D011897:Random Allocation; D051381:Rats; D012039:Regional Blood Flow / Q000187:drug effects; D012079:Renal Circulation / Q000187:drug effects; D013610:Tachycardia / Q000139:chemically induced; D014667:Vasopressins / Q000494:pharmacology
D000959:Antihypertensive Agents; D010446:Peptide Fragments; D010455:Peptides; D014667:Vasopressins; D000804:Angiotensin II; C058636:calcitonin gene-related peptide (8-37); D053607:Adrenomedullin; D009569:Nitric Oxide; D001120:Arginine; D015740:Calcitonin Gene-Related Peptide; D019331:NG-Nitroarginine Methyl Ester