Ain-Shoka A A, Buckner C K
Arch Int Pharmacodyn Ther. 1978 Apr;232(2):269-78.
Isoproterenol (10(-5) and 10(-4)M) inhibited a low affinity but not a high affinity form of rat heart cyclic AMP phosphodiesterase. The concentrations of isoproterenol required to produce inhibition of the isolated enzyme were 10,000 to 100,000 fold larger than those required to produce a positive chronotropic response in the isolated atria. Another beta adrenergic receptor agonist, soterenol, had no effect on any of the isolated forms of the enzyme. Theophylline produced inhibition of low and high affinity forms of phosphodiesterase at the same concentrations required to produce a positive chronotropic response in the isolated atria. Results from two experimental models failed to reveal any circumstances under which a contribution to the positive chronotropic response could result from isoproterenol-induced inhibition of cyclic AMP phosphodiesterase.
异丙肾上腺素（10⁻⁵和10⁻⁴M）抑制大鼠心脏环磷酸腺苷磷酸二酯酶的低亲和力形式，但不抑制高亲和力形式。抑制分离酶所需的异丙肾上腺素浓度比在分离心房中产生正性变时反应所需的浓度大10000至100000倍。另一种β肾上腺素能受体激动剂索特仑对该酶的任何分离形式均无影响。茶碱在分离心房中产生正性变时反应所需的相同浓度下，抑制磷酸二酯酶的低亲和力和高亲和力形式。两个实验模型的结果未能揭示任何情况下异丙肾上腺素诱导的环磷酸腺苷磷酸二酯酶抑制可导致正性变时反应。
