[Comparative study of cyclic nucleotide phosphodiesterase activity in the rabbit and bovine heart]

Activities of cyclic nucleotide phosphodiesterases (PDE) were studied in partially purified preparations from bovine and rabbit heart tissues. The PDE activity from rabbit heart was not increased in the course of purification and remained distinctly lower as compared with the enzymatic activity from bovine heart. Specific chelating agent Ca2+-EGTA (5 X 10(-4)M) inhibited effectively the PDE activity from bovine heart both in the ammonium sulfate fraction and in the fractions obtained by means of gel filtration on Sepharose 6B, but affected only slightly the enzyme activity from rabbit heart. The enzyme from bovine heart appears to involve mainly the Ca2+-calmodulin -dependent form, while the enzyme from rabbit heart, isolated under similar conditions, was Ca2+-calmodulin -independent. Phenothiazine derivatives inhibited distinctly the PDE activity from bovine heart at 5 X 10(-5)M concentration, whereas they did not affect or affected only slightly the enzyme preparations from rabbit heart even at 1 X 10(-4)M concentration; the inhibition was of the calmodulin -unspecific type. Phenothiazine derivatives (inhibitors of the calmodulin activity) exhibited only slight effect on the Ca2+-calmodulin -independent PDE from rabbit heart. This enzyme could not be used in studies of drugs, the effect of which is realized via regulation of the enzymatic activity by means of Ca2+ and calmodulin.