Different effects of histamine h1 and h2 stimulation on left
ventricular contractility in pigs.
Cooper, D. James, R. Robert Schellenberg, Keith R. Walley.
University of British Columbia, Pulmonary Research Laboratory, St.
Paul's Hospital, Vancouver, British Columbia, V6Z 1Y6, Canada
APStracts 2:0138H, 1995.
Histamine decreases ventricular contractility in some settings but
increases it in others. To better understand these apparently
discrepant results we measured hemodynamics and left ventricular
pressure (Millar catheter) and volume (ultrasonic crystals) in
atrially paced and [alpha]- and [beta]-antagonist treated pigs.
Histamine was infused (0.5 - 10 [mu]g x kg-1 x min-1) before and
after H2 antagonist (ranitidine) pretreatment. Changes in left
ventricular contractile function were measured as shift of the end
-systolic pressure-volume relationship at a pressure of 100 mmHg
([delta]ESPVR). We found that at low doses (0.5 and 1 [mu]g x kg-1 x
min-1) histamine significantly decreased left ventricular
contractility ( ESPVR -1.1 +/- 1.4 ml, p<0.05) after H2 antagonist
pretreatment. At doses above 1 [mu]g x kg-1 x min-1 histamine
increased contractility in a dose-response fashion (maximum effect
5.1 +/- 3.3 ml, ED50 0.75 +/- 1.79 [mu]g x kg-1 x min-1) best
described using a Hill coefficient of 2. Ranitidine increased the
ED50 by approximately one order of magnitude (0.75 +/- 1.79 to 9.50
+/- 2.60 [mu]g x kg-1 x min-1, p<0.05). We conclude that in vivo at
higher doses histamine increases left ventricular contractility via
H2 receptor stimulation while at low doses histamine decreases left
ventricular contractility, probably via H1 receptor stimulation.
Received 8 September 1994; accepted in final form 31 March 1995.
APS Manuscript Number H815-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 19 April 1995.