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To investigate the role of calcium-sensing receptor (CaSR) in the decrease of cardiac function in type 2 diabetic rats.Wistar rats were randomly divided into 3 groups including control, diabetic-4 week and diabetic-8 week groups. Rats in the diabetes group were fed with high-glucose and high-fat diet, and intraperitoneal injection of streptozocin (STZ,30 mg/kg) was conducted 4 weeks later to establish a type 2 diabetes model. Cardiac morphological changes were observed by HE staining, cardiac function was detected by echocardiography, and CaSR and PKC-αprotein expressions in cardiac tissue were detected by Western blot.Compared with the control group, the myocardium of diabetic rats showed irregular contraction zone, decreased expression of CaSR protein, increased expression of PKC-α protein, decreased systolic and diastolic functions, and gradually worsened with the prolongation of the course of the disease.Hyperglycemia inhibits the expression of CaSR protein in myocardium of diabetic rats by activating PKC-α, which can cause intracellular calcium disorder and lead to decreased cardiac function.

To observe the dynamic expression of calcium-sensing receptor(CaSR) in myocardium of diabetic rats.Thirty male Wistar rats were randomly divided into 3 groups including control, diabetic-4 week and diabetic-8 week groups(n = 10). The type 2 diabetes mellitus models were established by intraperitoneal injection of streptozotocin (STZ, 30 mg/kg) after high-fat and high-sugar diet for one month. The cardiac morphology was observed by electron microscope. Western blot analyzed the expression of CaSR, phospholamban (PLN), a calcium handling regulator, and Ca+-ATPase(SERCA) in cardiac tissues.Compared with control group, the expressions of CaSR and SERCA were decreased, while the expression of PLN was significantly increased in a time-dependent manner in diabetic groups. Meanwhile diabetic rats displayed abnormal cardiac structure.These results indicate that the CaSR expression of myocardium is reduced in the progression of DCM, and its potential mechanism may be related to the imnaired intracellular calcium homeostasis.

To study the effects of dopamin receptors-2 (DR2) on myocardial ischemic postconditioning and explore its underlying mechanisms.The myocardial ischemic postconditioning (PC) model was established in cultured primary rat neonatal cardiomyocytes which were then randomly assigned in the following groups: Nomial control group, Isehemia/reperfusion (L'R) group, PC (ischemic postconditioning) group, PC + Bro (Bromocriptine, a DB2 antagonist) group, PC + Hal (Haloperidol, a DB2 repressor) and PC + Hal + Bro groups. The lactate dehydrogenase (LDH) and superoxide dismutase (SOD) activity and malondialdehyde (MDA) content in cell medium were analyzed by colorunetry. The cell ultrastructure changes were observed by transmission electron microscope. The cell apoptosis was analyzed using flowcytometiy. The protein expression level of D112 and activity of p-p38 and p-JNK were detected by Western blot.Compared with the nonnal control group, hR increased the protein expression level of DB2, enhanced LDH activity and MDA content, promoted cell injury and apoptosis, decreased SOD activity, up-regulated the activity of p-p38 and p-JNK. Compared with the hR group, although PC further increased the expression of DR2 protein, it decreased LDH activity and MDA content, cell injury and apoptosis, increased SOD activity, down-regulated activity of p-p38 and p-JNK. Bromocriptine treatment further enhanced PC-induced canlioprotective effect, yet Hal addition attenuated this enhancing effect exerted by bromocriptine.The activation of DB2 is involved in the protective effect of ischemic postconditioning on myocardial ischemia/reperfusion injury through down-regulating the activity of p-p38 and p-JNK.

To observe the effect of dopamine receptor (DR2) activation on hypoxia/reperfusion injury (HRI) in the neonatal rat cardiomyocytes, and to explore its mechanism.The hypoxia/reperfusion (H/R) injury model was established in primarily cultured neonatal rat cardiomyocytes, and randomly assigned: control, H/R, bromocriptine (Bro) and haloperidol (Hal) groups. The cell apoptosis was detected using inverted microscope, transmission electron microscope and flow cytometry (FCM). The lactate dehydrogenase(LDH) and superoxide dismutase (SOD) activity and malondialdehyde (MDA) content in cell medium were analyzed. The expression of mRNA and protein of caspase-3, caspase-8, caspase-9, Fas, Fas-L, Cyt C and Bcl-2 were detected by RT-PCR and Western blot, respectively.Compared with the control group, apoptosis rate, LDH activity, MDA content and the expression of pro-apoptotic factors and anti-apoptotic factors were increased, but SOD activity was decreased in H/R group. Compared with the H/R group, all index above-mentioned were down-regulated or reversed in Bro-group, and had no obvious differences in Hal-group.The neonatal rat cardiomyocytes injury and apoptosis caused by hypoxia/reperfusion can be inhibited with DR2 activation, which mechanism is related to scavenging oxygen radical.

Activation of the calcium-sensing receptor (CaSR) leads to an increase of intracellular calcium concentration and alteration of cellular activities. High level of intracellular calcium is involved in hypoxia-induced proliferation of pulmonary arterial smooth muscle cells (PASMCs). However, whether the CaSR is expressed in PAMSCs and is related to the hypoxia-induced proliferation of PASMCs is unclear. In this study, the expression and distribution of CaSRs were detected by RT-PCR, western blotting and immunofluorescence; the intracellular concentration of free calcium ([Ca(2+) ](i) ) was determined by confocal laser scanning microscopy; cell proliferation was tested using an MTT and BrdU incorporation assay; cell cycle analysis was carried out using a flow cytometric assay; and the expression of proliferating cell nuclear antigen (PCNA), extracellular signal-regulated protein kinase 1,2 (ERK1,2) and AKT were analysed by western blotting. We observed that both CaSR mRNA and protein were expressed in rat PASMCs. Lowering of oxygen from 21% to 2.5% led to increased [Ca(2+) ](i) and CaSR expression. This condition of hypoxia also stimulated PASMCs proliferation accompanying with increased phosphorylation of ERK1,2 and AKT. GdCl(3) (an agonist of CaSR) or NPS2390 (an antagonist of CaSR) amplified or weakened the effect of hypoxia, respectively. PD98059 (a MEK1 inhibitor) or LY294002 (a PI3K inhibitors) decreased the up-regulation of PCNA expression and the increase of the cell proliferation index induced by hypoxia and GdCl(3) in PASMCs. Our results suggest that CaSR is expressed in rat PASMCs, and that CaSR activation through MEK1/ERK1,2 and PI3 kinase pathways is involved in hypoxia-induced proliferation of PASMCs.

To observe the effect of hyperlipidemia and atherosclerosis on rat myocardial expression of calcium-sensing receptor and apoptosis.The rat atherosclerosis model was induced by intraperitoneal injection of VD(3) (6 x 10(5) U/kg) and high cholesterol diet. Wistar rats were divided into two groups: (1) Control group; (2) AS group (n = 12 each). The expressions of CaSR, Bcl-2, Bax and caspase-3 were analyzed by Western blot and RT-PCR. Apoptotic cells were observed by TUNEL assay. The morphological changes of abdominal aorta and cardiac tissues were observed under optical and electro microscopes. The activity of LDH, CK, SOD and the content of MDA were assayed with ultraviolet spectrophotometer. The level of cTnT was detected by electrochemical immunofluorescence.Compared with control group, the activity of LDH and CK, the content of MDA and cTnT, the apoptosis index, the expression of CaSR, Bax and caspase-3 were significantly increased, but the SOD activity and Bcl-2 expression were significantly decreased, the myocardial ultrastructure injury was significantly aggravated in the AS group (all P0.05).Hyperlipidemia and atherosclerosis can up-regulate myocardial calcium-sensing receptor expression, promote myocardial apoptosis, aggravate oxidative stress and myocardial ischemia.

To observe the polyamines metabolism changes in rat cardiomyocytes underwent ischemia-reperfusion (I/R) injury.A branch of the descending left coronary artery was occluded to induce rat myocardial I/R injury (30 min ischemia followed by 2 h, 6 h, 12 h, and 24 h reperfusion). RT-PCR and Western blot were performed to detect the expression of spermidine/spermine N1-acetyltransferase (SSAT) and ornithine decarboxylase (ODC), the concentrations of polyamines were measured with high performance liquid chromatography in hearts with or without I/R.The myocardial transcription and expression of SSAT and ODC were significantly upregulated. Compared with the sham group, ODC mRNA and SSAT mRNA respectively increased 3.1 fold and 3.8 fold and their proteins respectively increased 3.1 fold and 2.9 fold at 24 h of reperfusion (P0.01); the concentrations of spermidine, spermine and the total polyamine pool respectively decreased by 33.6%, 35.3% and 32.9% while putrescine concentration increased by 58.9% at 24 h of reperfusion (P0.01).Our results suggest that ischemia-reperfusion in the heart may affect polyamine metabolism and the disturbance of polyamine metabolism might thus play a critical role in myocardial I/R injury in this model.

To observe the effect of artemisinin on the ischemia/reperfusion injury of the iisolated rat myocardium and to preliminarily study the possible mechanism.Fifty Wistar rats were randomly divided into 5 groups: a control group, an ischemia/reperfusion (I/R) group, and 3 artemisinin (AS) groups (10, 100, 1000 micromol x L(-1)), 10 rats in each group. Ischemia/reperfusion injury of the isolated rat myocardium was induced by a Langendorff system. The electrocardiogram, the cardiac functional parameters, coronary flow, and the activities of LDH (lactate dehydrogenase), CPK (creatine phosphokinase), SOD (superoxide dis-mutase) and the level of malondiadehyde (MDA) in myocardial tissue, and the myocardial ultrastructures were investigated.AS (10,100 micromol x L(-1)) could significantly improve the index of the myocardial function (+/- dp/dt(max), LVSP) after the ischemia/reperfusion, increase the coronary flow, decrease the leakage of LDH and CPK, and increase the SOD activity and decrease the MDA level in cardiac tissues, and alleviate the myocardial ultrastructure injury. But, AS (1000 micromo x L(-1)) did not have the above effects.AS (10, 100 micromol x L(-1)) alleviate the myocardial ischemia/reperfusion injury in rats. The mechanism may be related to its functions of antioxidation and scavenging free radicals.

To investigate the relaxative characteristics of resveratrol on thoracic aortic artery in the rat and its mechanism.We perfused the isolated rings and observed the response of NA-induced artery contraction to resveratrol under the Ca2+-contained and Ca2+-free bath solutions. In the same way were the effect of reveratrol on the vascular smooth muscle observed by adding two different concentration of KCl (30 and 80 mmol x L(-1)), and the effect on the contraction of the vascular smooth muscle depending on the intracellular calcium and extracellular calcium were also observed by adding NA. We also observed the effect of resveratrol on the contraction of rings induced by NA in the presence of L-NNA and Glibenclamide.Resveratrol relaxed rat aorta rings precontracted by NA in a dose-dependent manner. The relaxant effect of resveratrol on the rat rings of endothelium-denuded group was reduced compared with that of endothelium-intact group; the relaxant effect of resveratrol on rat rings was higher under the condition of Ca2+-free bath solution than that under the condition of Ca2+-contained bath solution. Resveratrol had a repressive effect on the aorta's contraction induced by intracellular calcium, but had no effect induced by extracellular calcium. Resveratrol relaxed the contractions induced by KCl 30 mmol x L(-1) as well as KCl 80 mmol x L(-1), but the contraction curve of KCl 80 mmol x L(-1) was shifted upward significantly. In the L-NNA group, the relaxant effect was attenuated by (26.0 +/- 4.6) %; but there was no change in the group of Glibenclamide ( P0.05).The results indicate that resveratrol relaxes vascular smooth muscle in an endothelium dependent manner. The mechanisms for this phenomenon seem to be related with promoting synthesis and release of NO, opening Ca2+ activated K+ channel (KCa channel) as well as the inhibition of Ca2+ influx and release of Ca2+ from intracellular stores.