Role of bcl-2 transcriptional regulation induced by calmodulin I pressure overload rat hypertrophic hearts / 生理学报

This study was designed to evaluate the role of bcl-2 transcriptional regulation induced by calmodulin I (CaM I) in pressure overload rat hypertrophic hearts. The model of hypertensive Sprague-Dawley rat was established by abdominal aortic constriction. The hearts were collected four weeks after abdominal aortic constriction. Velocity and isopyknic gradient centrifugation was employed to fractionate rat myocardial nuclei. Western blot analysis revealed a marked increase in phosphorylated cAMP response-element binding protein (pCREB) of cardiac hypertrophy group compared with that in control group (P<0.05), while the protein level of cAMP response-element binding protein (CREB) was constant (P>0.05). Immunohistochemistry results showed a significant increase of CaM I protein in cardiac hypertrophy group relative to the control group (P<0.05). Nuclear run off transcription assay displayed a significant increase in bcl-2 mRNA treated with trifluoperazne compared with non-drug treatment (P<0.05). The results obtained suggest that the transcription of bcl-2 is possibly regulated by CaM I hypertrophic rat hearts, and CREB phosphorylation seems to be a minor factor in bcl-2 transcriptional regulation.

Effects of angiotensin II on Ca2+ signal in cultured rat cardiac myocytes revealed by confocal laser scanning microscopy / 中国应用生理学杂志

<p><b>AIM</b>The effects of angiotensin II on the changes of Ca2+ signal in cultured rat neonatal myocytes were investigated in order to reveal the localization and distribution of elementary Ca2+ signaling units.</p><p><b>METHODS</b>The cultured neonate rat myocytes were treated with angiotensin II, and calcium signal was detected using confocal laser scanning microscopy and fluo-4/AM calcium probe.</p><p><b>RESULTS</b>The propagation of Ca2+ waves was observed in rest and angiotensin II stimulated cardiac myocytes. Calcium fluorescent intensity oscillated slightly in myocytes and the average intensity was much higher in the nucleus than in the cytosol, all of which could be magnified significantly by AngII (10(-6) mol/L). Ca2+ oscillation induced by Ang II was completely blocked by NO donor sodium nitroprusside. AngII evoked Ca2+ sparks close to the cell surface membrane, and couldn't be abolished by sodium nitroprusside.</p><p><b>CONCLUSION</b>There are spatiotemporal dynamics of Ca2+ signaling patterns such as Ca2+ wave, Ca2+ spikes, Ca2+ oscillation and the whole cell Ca2+ transients induced by angiotensin II, which might play very important roles in cellular cardiac function.</p>

The roles of nuclear Ca2+/CaM dependent kinases and calcineurin on the development of myocardial hypertrophy in rat / 中国应用生理学杂志

<p><b>AIM</b>To evaluate whether protein phosphorylation and dephosphorylation in nuclei play roles in the development of myocardial hypertrophy, distribution of protein kinases and phosphatases in cell fractions were determined.</p><p><b>METHODS</b>The model of hypertensive rat was established by abdominal aortic constriction. Velocity and isopyknic gradient centrifugation was employed to fractionate rat myocardium to membrane, cytosol and nuclei. Enzymatic methods were employed to determine kinases and phosphatases.</p><p><b>RESULTS</b>Compare with control group, the activity of CaMK increased by 101.1% (P < 0.01) and 40.16% (P < 0.01) respectively in nuclear and membranous fractions, changed without significance in cytosolic fraction; the activity of calcineurin in nuclei increased by 43.57%, (P < 0.05), lightly changed without significance in membranous and cytosolic fractions.</p><p><b>CONCLUSION</b>Nuclear translocation of CaMK and calcineurin, might play important roles on overload-induced cardiac hypertrophy.</p>

Comparison of ryanodine binding to cardiac sarcoplasmic reticulum and nuclear envelope of rat / 中国应用生理学杂志

<p><b>AIM</b>The characteristics of ryanodine receptor in rat cardiac sarcoplasmic reticulum (SR) and nuclear envelope (NE) were studied.</p><p><b>METHODS</b>Velocity and isopyknic gradient centrifugation was employed to fractionate rat SR and NE. Ryanodine receptor was assayed with [3H] ryanodine saturate binding to the preparations.</p><p><b>RESULTS</b>The maximal binding (Bmax) and dissociating constant (Kd) of ryanodine receptor in rat cardiac NE were, 1.7% and 60% of those in SR respectively. Phosphorylation in vitro by PKA and PKC increased Bmax of the receptors in SR by 372% and 121%, and augmented those in NE by 221% and 306%, without any effects on Kd.</p><p><b>CONCLUSION</b>Ryanodine receptors were present in rat myocardial NE, with lower density and higher affinity than those located in SR, which can be activated by PKA and PKC.</p>