Characterization of a stimulatory adenosine a2a receptor in adult
rat ventricular myocyte.
Xu, Hao, Birgitt Stein, and Bruce Liang.
Department of Medicine, Cardiovascular Division, University of
Pennsylvania Medical Center, Philadelphia, PA and Department of
Pharmacology, Universitats-Krankenhaus Eppendorf, Hamburg,
Germany
APStracts 2:0461H, 1995.
The expression and function of stimulatory adenosine A2 receptor on
the cardiac myocyte is not well-defined. The objective of the present
study is to characterize the adenosine A2a receptor in adult rat
cardiac ventricular myocytes. After selection of an optimal lot of
collagenase for myocyte isolation and for consistent measurement of
adenosine-mediated responses, adenosine A1 receptor pathway was
inactivated by pertussis toxin and by A1-selective antagonist DPCPX.
Effects of adenosine agonist and antagonist on cardiac myocyte
contractile amplitude and on cAMP levels were determined. The A2a
receptor-selective agonist 2-[4-(2-carboxyethyl)phenylethylamino]-5'
-N-ethylcarboxamidoadenosine (CGS21680) caused a pronounced
stimulation of myocyte contractile amplitude and an increase in the
cAMP level, as did the nonselective agonists N-ethyladenosine-5'
-uronic acid and adenosine. The A2a receptor-selective antagonist 8
-(3-chlorostyryl)caffeine blocked the NECA- and adenosine-induced
positive inotropic response. Probing of myocyte RNA with a rat A2a
receptor cDNA demonstrated a 2.6 kb mRNA, corresponding to that
encoding the A2a receptor. Together, data from contractile, cAMP and
RNA studies indicate that adenosine A2a receptors are expressed and
are functionally coupled to stimulaton of cAMP accumulation and
cardiac contractility in adult rat ventricular myocyte.
Received 5 July 1995; accepted in final form 26 September 1995.
APS Manuscript Number H611-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 November 95