Augmentation of cardiac contractility with no change in L-type Ca2+ current in transgenic mice with a cardiac-directed expression of the human adenylyl cyclase type 8 (AC8)

作者：Georget M; Mateo P; Vandecasteele G; Jurevicius J; Lipskaia L; Defer N; Hanoune J; Hoerter J; Fischmeister R^*

来源：The FASEB Journal, 2002, 16(10): 1636-+.

DOI：10.1096/fj.02-0292fje

• cAMP
• isolated heart
• calcium transient
• cell shortening
• compartmentation

The beta-adrenergic cascade is severely impaired in heart failure(HF), in part because of a reduction in the activity of the two dominant cardiac adenylyl cyclase (AC) isoforms, AC5 and AC6. Hence, cardiac-directed AC overexpression is a conceivable therapeutic strategy in HF. In this study, we explored the consequences at the cellular and organ level of a cardiac-directed expression of the human AC8 in the transgenic mouse line AC8TG. Unlike AC5 and AC6, which are inhibited by intracellular Ca2+, AC8 is stimulated by Ca2+-calmodulin. Langendorff perfused hearts from AC8TG mice had a twofold higher left ventricular systolic pressure, a 40% faster heart rate, a 37% faster relaxation, and a 30% higher sensitivity to external Ca2+ than nontransgenic control mice (NTG). Cell shortening measured in isolated ventricular myocytes developed 22% faster and relaxed 43% faster in AC8TG than in NTG mice. Likewise, Ca2+ transients measured in fluo-3 AM-loaded myocytes were 30% higher and relaxed 24% faster in AC8TG compared with NTG mice. In spite of the large increase in Ca2+ transients and contraction, expression of AC8 had no effect on the whole-cell L-type Ca2+ current (I-Ca,I-L) amplitude. Moreover, I-Ca,I-L was unchanged even when AC8 was activated by raising intracellular Ca2+. Thus, cardiac expression of AC8 leads to an increase in cAMP that activates specifically Ca2+ uptake into the sarcoplasmic reticulum but not Ca2+ influx at the sarcolemma, suggesting a strong compartmentation of the cAMP signal.

• 出版日期2002-8