it has also been observed that phosphorylation of seryl residues of protein in sarcolemma- and sarcotubule-rich myocardial subcellular fractions by cyclic amp activated intrinsic and extrinsic protein kinases confers upon these membran structures an enhanced ability to bind or take up ca2+ and that dibutyryl cyclic amp , like adrenaline , produces in intact cardiac muscle simultaneous increases in contractile force and in the uptake of extracellular ca2+ .
C0001455
cyclic amp
C0012054
dibutyryl cyclic