压力超负荷下大鼠心肌细胞核钙调节系统的变化

目的：通过腹主动脉缩窄（abdominal aortic coaretation，AAC）心肌肥厚大鼠模型制备、差速离心提纯心肌细胞核、酶学方法测定Ca^2＋-ATPase活性、^45Ca^2＋同位素法测定核钙摄取和^3H放射配基受体分析心肌细胞核膜IP3R和RyR的动力学特性，初步揭示压力超负荷心肌肥厚大鼠心肌细胞核钙转导异常的环节。结果发现：AAC术后4周大鼠心肌显著肥厚，伴有明显的血流动力学异常，与对照组比较，AAC大鼠心肌细胞核Ca^2＋-ATPase活性减少51．93％（P〈0．001），但核^45Ca^2＋摄入量（核外Ca^2＋]浓度为800-1600nmol／L时）明显增加（P〈0．05）；AAC大鼠心肌细胞核IP3R的Bmax和Kd与对照组比较分别增加1．217和2．149倍（P〈0．01），其细胞核RyR的最大结合（Bmax）较对照组减少57．8％（P〈0．001），解离常数（Kd）较对照组降低54．4％（P〈0．05）。结论为心肌细胞核Ca^2＋转运系统发生改变（Ca^2＋．ATPase活性减少、核^45Ca^2＋摄取增加、IP3R密度上调和亲和力降低，而细胞核RyR密度下调而亲和力增加），可能参与压力超负荷心肌肥厚的发生过程。

Alterations of calcium transport system in nuclear envelopes of myocardium involved in pressure overload-induced hypertrophy of rat heart

Objective The hypertrophy rat model was established by abdominal aortic constriction and velocity and isopyknic gradient centrifugation was employed to fractionate the cardiac nuclei.The alterations in Ca~(2 )-ATPase activity and ()~(45)Ca~(2 ) uptake as well as Maximal number of binding sites (B max)and dissociation constant (Kd)of IP 3 and ryanodine to the nuclear envelopes were measured.Our results show that (1)the Ca~(2 )-ATPase in cardiac nuclei was decreased by 51.93% (p<0.001).()~(45)Ca~(2 ) uptake were significantly augmented in the range of 800-1600nmol/L of incubating free (p<0.05)compared with those of control.(2)B max and Kd of IP 3Rs on myocardial nuclear envelope were increased by 1.217 (P<0.01)and by 2.149-fold (P<0.01)respectively in hypertrophic myocardium as compared with those of the control.(3)Existence of RyRs on myocardial nuclear envelope was proved.Both Bmax and Kd of ryanodine binding decreased by 57.8% (P<0.001)and by 54.4%(P<0.05)respectively in hypertrophic myocardium compared with those in control.These results suggested that the alterations in calcium transport system in the myocardial nuclei may be partly responsible for the modified cardiac function in pressure overload-induced cardiac hypertrophy.