溶血磷脂酸对幼年大鼠心肌细胞收缩和钙瞬变的影响

目的我们前期的研究发现LPA受体在幼年大鼠心脏的表达显著高于成年的表达,提示LPA信号在心脏收缩功能尚未成熟时可能具有更为重要的调节作用。本研究通过观察LPA对此未成熟阶段心肌细胞钙瞬变和收缩力的作用,探讨LPA信号对幼年心肌兴奋-收缩耦联的影响。方法 Langendorff装置逆向灌流胶原酶分离获得不同发育阶段大鼠心肌细胞;采用IonOptix细胞收缩和钙离子浓度同步测定系统进行心肌细胞收缩力和钙瞬变的测定;Western blot检测不同发育阶段心肌细胞LPA受体的表达。结果 LPA对出生后14天和21天大鼠心肌细胞的收缩和钙瞬变均没有显著影响,表明LPA信号并不参与出生后14-21天大鼠心肌细胞的兴奋-收缩耦联过程和心肌细胞收缩。在大鼠出生后发育过程中,LPA受体在心肌细胞的表达在出生后14天已显著下调,不同于在整体心脏表达下调的时间点(P21d),这可能是LPA对此发育阶段心肌细胞的收缩和钙瞬变均不产生影响的原因,提示在出生后14天LPA信号对心肌细胞的发育调节功能可能即已减弱或消失。结论 LPA信号对出生后14天及之后心肌收缩和钙瞬变无显著影响,但尚不能排除LPA对出生后更早期的未成熟心肌细胞收缩和兴奋-收缩耦联的作用。

Effect of Lysophosphatidic Acid in Contraction and Excitation-Contraction Coupling of Immature Cardiomyocyte

Objective Our previous study showed that expression levels of Lparl, Lpar3, and Lpar4 were significantly elevated around birth compared to the adult heart and remained elevated for the first two weeks of postnatal life before downregulating significantly to a very low adult level of expression by P21 d. This decreased expression starting at P21 d may correlate with mature systolic function of the rat heart. The present study is to investigate that LPA involved in contraction and excitation-contraction coupling by inducing calcium mobilization in immature cardiomyocytes. Methods For preparation of cardiomyocytes from juvenile rats, hearts were isolated by traditional and improved Langendorff perfusion. Effect of LPA in contraction and intracellular calcium transient in individual myocardial cell was measured by Myocyte Calcium and Contractility Recording System （IonOptix, USA）. Changes in LPA receptors protein expression during postnatal cardiac development were detected by Western blot. Results LPA had no effect on the contraction and calcium transient in isolated cardiomyocytes at postnatal 14 and 21 days of age. Western blot analysis showed that the expressions of Lparl, Lpar3 and Lpar4 were down-regulated at P14d, which was not paralleled the developmental changes of these three receptors in whole heart. It suggests that LPA signaling have lost the effect of developmental modulation in cardiomyocytes at P14d. Conclusion LPA signaling was not involved in contraction and excitation-contraction coupling in the cardiomyocytes when the expressions of LPA receptors were down-regulated.