Dibutyryl cyclic AMP and adrenaline increase contractile force and 45Ca uptake in mammalian cardiac muscle

Summary The effects of dibutyryl cyclic AMP (DB-AMP; 10^–3M) and adrenaline (2.2×10^–6 M) on contractile force, ⁴⁵Ca uptake, and total myocardial Ca concentration were investigated in electrically driven left auricles isolated from rat hearts. The experiments were performed at an extracellular Ca concentration of 0.45 mM and at low frequency of stimulation (15 beats/min). ⁴⁵Ca exposure was 5 min. Under the conditions used, both drugs increased contractile force and enhanced ⁴⁵Ca uptake (expressed as relative specific activity) by about 30% (DB-AMP) and 40% (adrenaline), respectively. Thus, the results provide evidence that the effects of adrenaline on ⁴⁵Ca uptake in mammalian cardiac muscle can be mimicked by DB-AMP.