Catecholamines and preconditioning: studies of contraction and function in isolated rat hearts.. Hearse, David J., and Fiona J. Sutherland. Cardiovascular Research, The Rayne Institute, St. Thomas' Hospital, London SE1 7EH.
APStracts 6:0156H, 1999.
The aims were to determine whether: (i) like ischemic preconditioning, transient exposure to noradrenaline prior to ischemia exacerbates contracture during ischemia and (ii) protection afforded by noradrenaline is stereospecific (receptor-mediated). Isolated perfused rat hearts were randomised into 5 groups (n=6/group): (i) ischemic preconditioning (3 min ischemia + 3 min reperfusion + 5 min ischemia + 5 min reperfusion), (ii) untreated control, (iii) vehicle control (ascorbic acid), (iv) substituting preconditioning ischemia by perfusion with D noradrenaline and ( v) substituting preconditioning ischemia by perfusion with L noradrenaline. This was followed by 40 min of zero-flow ischemia and 50 min reperfusion. Ischemic preconditioning and L-noradrenaline exacerbated contracture (time-to-50% contracture = 9.2 +/- 1.1 and 9.0 +/- 1.1 vs 13.3 +/- 0.3, 12.4 +/- 0.5 and 13.2 +/- 0.4 min for untreated control, vehicle control and D-noradrenaline respectively, p<0.05). Post-ischemic LVDP was poor in untreated controls (23.0 +/- 2.2%), vehicle controls (26.9 +/- 2.3%) and D-noradrenaline (19.8 +/- 2.8%) groups but good in preconditioned (52.4 +/- 5.1%) and L-noradrenaline (52.5 +/- 1.1%) groups (p<0.05). Thus noradrenaline preconditioning, like ischemic preconditioning, causes a paradoxical exacerbation of contracture coupled with enhanced post-ischemic recovery, both effects are stereospecific. 

Received 18 November 1998; accepted in final form 10 March 1999.
APS Manuscript Number H962-8.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1999 The American Physiological Society.
Published in APStracts on 22 March 1999