Luiken J J F P, Willems J, Coort S L M, Coumans W A, Bonen A, Van Der Vusse G J, Glatz J F C
Department of Physiology, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, NL-6200 MD Maastricht, The Netherlands.
Biochem J. 2002 Nov 1;367(Pt 3):881-7. doi: 10.1042/BJ20020432.
Recently, we established that cellular contractions increase long-chain fatty-acid (FA) uptake by cardiac myocytes. This increase is dependent on the transport function of an 88 kDa membrane FA transporter, FA translocase (FAT/CD36), and, in analogy to skeletal muscle, is likely to involve its translocation from an intracellular pool to the sarcolemma. In the present study, we investigated whether cAMP-dependent signalling is involved in this translocation process. Isoproterenol, dibutyryl-cAMP and the phosphodiesterase (PDE) inhibitor, amrinone, which markedly raised the intracellular cAMP level, did not affect cellular FA uptake, but influenced the fate of intracellular FAs by directing these to mitochondrial oxidation in electrostimulated cardiac myocytes. The PDE inhibitors 3-isobutyl-1-methylxanthine, milrinone and dipyridamole each significantly stimulated FA uptake as well as intracellular cAMP levels, but these effects were quantitatively unrelated. The stimulatory effects of these PDE inhibitors were antagonized by sulpho- N -succinimidylpalmitate, indicating the involvement of FAT/CD36, albeit that the different PDE inhibitors use different molecular mechanisms to stimulate FAT/CD36-mediated FA uptake. Notably, 3-isobutyl-1-methylxanthine and milrinone increased the intrinsic activity of FAT/CD36, possibly through its covalent modification, and dipyridamole induces translocation of FAT/CD36 to the sarcolemma. Elevation of intracellular cGMP, but not of cAMP, by the PDE inhibitor zaprinast did not have any effect on FA uptake and metabolism by cardiac myocytes. The stimulatory effects of PDE inhibitors on cardiac FA uptake should be considered when applying these agents in clinical medicine.
最近，我们证实细胞收缩可增加心肌细胞对长链脂肪酸（FA）的摄取。这种增加依赖于一种88 kDa膜脂肪酸转运蛋白——脂肪酸转位酶（FAT/CD36）的转运功能，并且与骨骼肌类似，可能涉及其从细胞内池转运至肌膜。在本研究中，我们调查了cAMP依赖性信号传导是否参与此转运过程。异丙肾上腺素、二丁酰环磷腺苷（dibutyryl-cAMP）以及磷酸二酯酶（PDE）抑制剂氨力农可显著提高细胞内cAMP水平，但并未影响细胞对FA的摄取，而是通过引导电刺激心肌细胞内的FA进行线粒体氧化来影响细胞内FA的去向。PDE抑制剂3-异丁基-1-甲基黄嘌呤、米力农和双嘧达莫均显著刺激FA摄取以及细胞内cAMP水平，但这些效应在数量上并无关联。这些PDE抑制剂的刺激作用可被硫代-N-琥珀酰亚胺基棕榈酸酯拮抗，表明FAT/CD36参与其中，尽管不同的PDE抑制剂通过不同的分子机制刺激FAT/CD36介导的FA摄取。值得注意的是，3-异丁基-1-甲基黄嘌呤和米力农可能通过共价修饰增加FAT/CD36的内在活性，而双嘧达莫可诱导FAT/CD36转位至肌膜。PDE抑制剂扎普司特可提高细胞内cGMP而非cAMP水平，对心肌细胞的FA摄取和代谢没有任何影响。在临床医学中应用这些药物时，应考虑PDE抑制剂对心脏FA摄取所产生的刺激作用。
