Kelso E J, McDermott B J, Silke B
Department of Therapeutics and Pharmacology, Queen's University of Belfast, U.K.
Biochem Pharmacol. 1995 Feb 14;49(4):441-52. doi: 10.1016/0006-2952(94)00476-3.
The intracellular actions of phosphodiesterase (PDE) inhibitors on the accumulation of cyclic nucleotides were studied in isolated ventricular cardiomyocytes from adult Sprague-Dawley rats. Elevated levels of cyclic AMP, due to the effects of selective PDE inhibitors, were detected only when the levels of cyclic nucleotide were enhanced with forskolin (10 microM). The time course for the elevation of cyclic AMP levels was similar for all the PDE inhibitors tested, following the pattern of an initial rise in the first 2-4 min, proceeded by a steady state at 67 +/- 6% of the maximum stimulation. HN-10200 (2-[3-methoxy-5-methylsulfinyl-2-thienyl]-1H-imidazo-[4,5-c]- pyridine hydrochloride), a new imidazopyridine derivative, had a similar concentration-dependent profile to the structurally related compound, sulmazole (AR-L 115 BS, 2-[2-methoxy-4-methylsulfinyl)phenyl]-1H- imidazo-[4,5-b]-pyridine). Both the non-selective inhibitor, 3-isobutyl-1-methylxanthine (IBMX), and the selective PDE IV inhibitor, Ro 20-1724 (4-[(3-butoxy-4-methoxyphenyl)methyl]-2- imidazolidinone), potentiated the forskolin-stimulated levels of cyclic AMP with a much greater efficacy than sulmazole or HN-10200. The concentrations of forskolin required by IBMX, sulmazole and HN-10200 (10(-3) M) to increase levels of cyclic AMP by 4 pmol/mg protein were 3.2 x 10(-6) M, 1.32 x 10(-5) M and 1.46 x 10(-5) M, respectively. Enoximone failed to cause an increase in the levels of cyclic AMP, even when stimulated with maximal concentrations of forskolin. Furthermore, in the presence of forskolin, enoximone attenuated the response of Ro 20-1724 and IBMX in a concentration-dependent manner. Enoximone, similarly to HN-10200, sulmazole, Ro 20-1724 and IBMX did not produce any significant effect on levels of cyclic GMP under elevated conditions in the presence of sodium nitroprusside. The combined action of Ro 20-1724, with either HN-10200, sulmazole, or IBMX (10(-4) M), on intracellular levels of cyclic AMP, was not greater than the response to Ro 20-1724 alone. These data demonstrate the differential actions of PDE III and PDE IV inhibitors in rat ventricular cardiomyocytes. It is suggested that enoximone has a high selectivity for the PDE III isoenzyme so that hydrolysis of cyclic AMP by the PDE IV isoenzyme is not inhibited, in accordance with the lack of increase in cyclic AMP by enoximone in rat cardiomyocytes. HN-10200 and sulmazole, producing small increases in intracellular levels of cyclic AMP, are less selective PDE III inhibitors than enoximone.(ABSTRACT TRUNCATED AT 400 WORDS)
在成年Sprague-Dawley大鼠分离的心室心肌细胞中研究了磷酸二酯酶（PDE）抑制剂对环核苷酸积累的细胞内作用。仅当用福斯可林（10 microM）提高环核苷酸水平时，才检测到由于选择性PDE抑制剂的作用而导致的环磷酸腺苷（cAMP）水平升高。所有测试的PDE抑制剂使cAMP水平升高的时间进程相似，在前2-4分钟呈现初始上升模式，随后在最大刺激的67±6%处达到稳定状态。新型咪唑吡啶衍生物HN-10200（2-[3-甲氧基-5-甲基亚磺酰基-2-噻吩基]-1H-咪唑并-[4,5-c]-吡啶盐酸盐）与结构相关化合物舒马唑（AR-L 115 BS，2-[2-甲氧基-4-甲基亚磺酰基）苯基]-1H-咪唑并-[4,5-b]-吡啶）具有相似的浓度依赖性特征。非选择性抑制剂3-异丁基-1-甲基黄嘌呤（IBMX）和选择性PDE IV抑制剂Ro 20-1724（4-[(3-丁氧基-4-甲氧基苯基)甲基]-2-咪唑烷酮）增强福斯可林刺激的cAMP水平的效力比舒马唑或HN-10200大得多。IBMX、舒马唑和HN-10200（10⁻³ M）使cAMP水平增加4 pmol/mg蛋白质所需的福斯可林浓度分别为3.2×10⁻⁶ M、1.32×10⁻⁵ M和1.46×10⁻⁵ M。依诺昔酮即使在用最大浓度的福斯可林刺激时也未能使cAMP水平升高。此外，在存在福斯可林的情况下，依诺昔酮以浓度依赖性方式减弱Ro 20-1724和IBMX的反应。与HN-10200、舒马唑、Ro 20-1724和IBMX类似，依诺昔酮在硝普钠存在的升高条件下对环磷酸鸟苷（cGMP）水平没有产生任何显著影响。Ro 20-1724与HN-10200、舒马唑或IBMX（10⁻⁴ M）联合对细胞内cAMP水平的作用不大于单独对Ro 20-1724的反应。这些数据证明了PDE III和PDE IV抑制剂在大鼠心室心肌细胞中的不同作用。提示依诺昔酮对PDE III同工酶具有高选择性，因此大鼠心肌细胞中依诺昔酮不会抑制PDE IV同工酶对cAMP的水解。HN-10200和舒马唑使细胞内cAMP水平略有升高，它们是比依诺昔酮选择性更低的PDE III抑制剂。（摘要截断于400字）
