ISSN:
1432-1912
Keywords:
Dibutyryl-c-AMP
;
Adrenaline
;
Isolated Rat Auricles
;
Positive Inotropic Effect
;
45Ca Exchange
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary The effects of adrenaline (2.2×10−6 M) and cyclic N6-2′-O-dibutyryl-adenosine-3′,5′-monophosphate (DB-c-AMP; 10−3 M) on mechanical performance, 45Ca uptake and total tissue calcium concentration were investigated in electrically stimulated left auricles isolated from female rats weighing 180–220 g. The experiments were performed at reduced [Ca]e of 0.45 mM and at various frequencies of stimulation (0–120 beats/min). In the first series of experiments 45Ca incubation time was 5 min. Under these conditions DB-c-AMP as well as adrenaline enhanced contractile force to 300–450% of the control values at all frequencies tested (Fig.1). This increase in contractile force was accompanied by a significant enhancement in 45Ca exchange (Fig.2) while the total tissue calcium concentration remained unchanged (Table 1). In resting auricles 45Ca exchange was not altered under the influence of both drugs. At long periods of 45Ca exposure (40–90 min) both drugs augmented contractile force in a way similar to that of the first series of experiments (Fig.4) but no influence of DB-c-AMP or adrenaline on 45Ca exchange could be detected (Fig.3). It is concluded that DB-c-AMP can mimic the wellknown effects of adrenaline on myocardial calcium movements. Under the assumption that DB-c-AMP is representative for c-AMP, the results thus provide experimental support for the view that the positive inotropic effect of adrenaline is mediated by primary changes in the intracellular level of c-AMP which secondarily might enhance calcium fluxes across the cardiac cell membrane.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00500798
