Changes of adrenomedullin 2/intermedin in the lung of rats with chronic hypoxic pulmonary hypertension / 中国应用生理学杂志

<p><b>AIM</b>To investigate the changes and probable roles of adrenomedullin2/intermedin (AIDM2/IMD), a novel micromolecular bioactive peptide, in the lungs of rats with chronic hypoxic pulmonary hypertension.</p><p><b>METHODS</b>Twenty male SD rats were randomly divided into normal control group (NC) and normobaric hypoxia group (4H). The protein levels of ADM and ADM2/IMD) in the plasma and lung were measured by radioimmunoassay and immunohistochemistry. The mRNA expressions of ADM, ADM2/IMD and their receptors C (RLR, RAMP1, RAMP2 and RAMP3 in the lung tissue were determined by reverse transcription-polymerase chain reaction (RT-PCR).</p><p><b>RESULTS</b>(1) The rat model of chronic pulmonary hypertension was confirmed by the increased mean pulmonary arterial pressure (mPAP) and weight ratio of right ventricle to left ventricle plus septum [RV/(LV + S)] in 4H group compared to NC group. (2) The concentrations of ADM in the plasma and lung homogenate of 4H group were 2.3 and 3.2 folds of NC group, respectively (all P < 0.01). The levels of ADM2/IMD were higher 89.6% and 45.0% in the plasma and lung homogenate of 4H group than those of NC group (respectively, P < 0.01, P < 0.05). (3) The mRNA expressions of ADM2/IMD and ADM in the lung of 4H group were up-regulated (respectively, P < 0.01, P < 0.05 vs. NC group). The expressions of CRLR and RAMP1 mRNAs were down-regulated (all P < 0.01 vs. NC group), while the levels of RAMP2 and RAMP3 mRNAs were no significant difference between the two groups. (4) The strong ADM2/IMD immunostaining was detected in the endothelial and adventitial cells of the rat pulmonary arteriole.</p><p><b>CONCLUSION</b>ADM2/IMD, like its paralog ADM, might be closely related to the chronic hypoxic pulmonary hypertension in rats. The disorders of the gene expression and/or the synthesis and metabolism of ADM2/IMD and its receptor CRLR/RAMP1 possibly take part in the pathogenesis of chronic hypoxic pulmonary hypertension in rats.</p>

Changes of intermedin/adrenomedullin 2 and its receptors in the right ventricle of rats with chronic hypoxic pulmonary hypertension / 生理学报

The purpose of the present study was to explore the expression changes of intermedin/adrenomedullin 2 (IMD/ADM2), a novel small molecular bioactive peptide, and its receptors, calcitonin receptor-like receptor (CRLR) and receptor activity modifying proteins (RAMP1, RAMP2, RAMP3) in the right ventricle of rats with chronic hypoxia-induced pulmonary hypertension. Twenty male Sprague-Dawley rats were randomly divided into 4-week hypoxia group and normal control group (each n=10). The rats in hypoxia group were placed in an isobaric hypoxic chamber, in which O(2) content was maintained at 9%-11% by delivering N(2), and CO(2) content was maintained at <3% for 4 weeks (8 h/d, 6 d/week). The rats in the control group were housed in room air. The protein levels of IMD/ADM2 and adrenomedullin (ADM) in blood plasma and right ventricular tissue were measured by radioimmunoassay. The mRNA expressions of IMD/ADM2, ADM and their receptors CRLR, RAMP1, RAMP2, RAMP3 in right ventricular tissue were determined by reverse transcription-polymerase chain reaction (RT-PCR). The results showed that the ratio of right ventricle weight to left ventricle plus septum weight [RV/(LV+S)] and mean pulmonary arterial pressure (mPAP) were higher in hypoxia group than those in the control group (all P<0.01), suggesting that the rat model of pulmonary hypertension was successfully established. However, the mean carotid arterial pressure (mCAP) between the two groups had no significant difference. Compared with that in the control group, ADM contents in plasma and right ventricular tissue in hypoxia group increased by 1.26 and 1.68 folds (all P<0.01), respectively. Likewise, IMD/ADM2 contents in blood plasma and right ventricular tissue in hypoxia group increased by 0.90 and 1.19 folds (P<0.01), respectively, compared with that in the control group. The data of RT-PCR showed that mRNA levels of ADM, IMD/ADM2 and RAMP2 in hypoxia group increased by 155.1% (P<0.01), 80.9% (P<0.01) and 52.9% (P<0.05), respectively, compared with those in the control group. There were no significant differences in mRNA expressions of CRLR, RAMP1 and RAMP3 between the two groups (all P>0.05). Taken together, the results show that the level of IMD/ADM2 increases in the rats with chronic hypoxia-induced pulmonary hypertension.

The signal transduction pathway in the proliferation of airway smooth muscle cells induced by urotensin II / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Human urotensin II (UII) is the most potent mammalian vasoconstrictor identified so far. Our previous study showed that UII is a potent mitogen of airway smooth muscle cells (ASMC) inducing ASMC proliferation in a dose-dependent manner. The signal transduction pathway of UII mitogenic effect remains to be clarified. This study was conducted to investigate the signal transduction pathway in the proliferation of ASMC induced by UII.</p><p><b>METHODS</b>In primary cultures of rat ASMCs, activities of protein kinase C (PKC), mitogen-activated protein kinase (MAPK) and calcineurin (CaN) induced by UII were measured. The effect of CaN on PKC and MAPK was studied by adding cyclosporin A (CsA), a specific inhibitor of CaN. Using H7 and PD98059, inhibitors of PKC and MAPK, respectively, to study the effect of PKC and MAPK on CaN. The cytosolic free calcium concentration induced by UII was measured using Fura-2/AM.</p><p><b>RESULTS</b>UII 10(-7) mol/L stimulated ASMC PKC and MAPK activities by 44% and 24% (P < 0.01), respectively, after incubating for 20 minutes. It increased CaN activity in a time-dependent manner, being 1.68 times as that of control for 24 hours (P < 0.01). It promoted the cytosolic free calcium concentration increase of 18% (P < 0.01). CsA 10(-6) mol/L and H7 50 micromol/L inhibited UII-stimulated CaN activity by 45% (P < 0.01) and 21% (P < 0.05), respectively, while PD98059 50 micromol/L had no effect on CaN activity (P > 0.05). CsA 10(-6) mol/L inhibited UII-stimulated PKC activity by 14% (P < 0.05), while having no effect on MAPK activity (P > 0.05).</p><p><b>CONCLUSIONS</b>UII increases cytosolic free calcium concentration and activates PKC, MAPK and CaN. The signal transduction pathway between PKC and CaN has cross-talk.</p>

Levels of adrenomedullin and proadrenomedullin N-terminal 20 peptide in myocardium and aorta of spontaneously hypertensive rats and Wistar-Kyoto rats / 生理学报

In this study, we observed the levels of adrenomedullin (ADM) and proadrenomedullin N-terminal 20 peptide (PAMP) in myocardium and aorta of spontaneously hypertensive rats (SHRs) in comparison with Wistar-kyoto (WKY) rats. Contents of ADM and PAMP were measured by radioimmunoassay (RIA) in plasma, myocardium and aorta. The amount of Pro-ADM mRNA of myocardium and aorta was determined by competitive quantitative reverse transcription polymerase chain reaction (RT-PCR). In SHRs the amounts of Pro-ADM mRNA of myocardium and aorta were 66.7% (P<0.01) and 73% (P<0.01) higher than those in WKY rat, respectively. In SHRs, the levels of ADM in plasma, myocardium and aorta were 29%, 76.7% and 79% (all P<0.01) higher than those in WKY rats, respectively. The level of PAMP in SHRs was increased by 42.5% in plasma (P<0.01), 47.2% in myocardium (P<0.0.1) and 27.3% in aorta (P<0.05) compared to WKY rats, respectively. In addition, the ratio of ADM content to PAMP content in SHRs group was increased compared with that in WKY group (2.0+/-0.25 vs 1.64+/-0.3 and 2.2+/-0.18 vs 1.56+/-0.28, in myocardium and aorta, respectively, P<0.01). These results suggest that ProADM gene expression is up-regulated and the increase in ADM and PAMP is different in SHRs. The significance of inconsistency of increase in ADM and PAMP in SHRs needs to be further investigated.

Hyperglycemia inhibited taurine transport and taurine transporter gene expression in cultured rat cardiomyocytes / 中国应用生理学杂志

<p><b>AIM</b>To investigate the alterations of taurine transport, and taurine transporter (TAUT) mRNA by hyperglycemia in cultured rat cardiomyocytes.</p><p><b>METHODS</b>3H-taurine measured the amount of taurine uptake. TAUT mRNA consents were measured using quantitative RT-PCR.</p><p><b>RESULTS</b>The cellular uptake amounts of taurine in seven groups increased with incubation time, and near to be saturated after 5 min. The uptake amount of 10, 20, and 30 mmol/L glucose groups was obviously lower than that of the control group (P < 0.05 or P < 0.01). In 30 mmmol/L glucose, taurine release obviously was decreased, as compared with that of the control. Exposure of cells to 10, 20, and 30 mmmol/L glucose decreased taurine uptake in a concentration-dependent fashion. Exposure to hyperglycemia did not affect the Km of the TAUT, but the apparent Vmax were significantly decreased (P < 0.05). In 20 and 30 mmmol/L groups, TAUT mRNA contents of myocardial cells were significantly reduced, as compared with the control group (P < 0.05).</p><p><b>CONCLUSION</b>The data suggests that there are dysfunction of taurine uptake and downregulation of TAUT gene expression by glucose in cultured rat cardiomyocytes.</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>

Effects of mitochondrial L-arginine/nitric oxide system on mitochondrial Ca2+ transport in rat myocardium / 中国应用生理学杂志

<p><b>AIM AND METHODS</b>To observe the effect of myocardial mitochondrial L-arginine (L-Arg)/nitric oxide (NO) system on mitochondrial Ca2+ transport by using purified rat mitochondria and incubation of them in vitro.</p><p><b>RESULTS</b>Compared with control group, incubation of mitochondria with L-Arg (10(-4) mol/L, NO substrate) or sodium nitroprusside (5 x 10(-7) mol/L, the donor of exogenous NO, SNP) increased significantly mitochondrial NO2- (66% and 89%, P < 0.01), respectively, and decreased the Ca2+ content (40% and 54%, P < 0.01). After L-Arg or SNP treatment, mitochondrial Ca2+ uptake were decreased by 67% and 85%, respectively (P < 0.01), vs control. The rate of mitochondrial Ca2+ release decreased by 11% and 8%, respectively (P < 0.01). When L-NAME (NO synthase inhibitor) was incubated with mitochondria and the L-Arg together, it inhibited the effects of L-Arg, NO2 on the mitochondrial NO2 formation, Ca2+ content descending, and decrease of Ca2+ uptake and release.</p><p><b>CONCLUSION</b>The data suggest that myocardial mitochondrial L-Arg /NO systems take part in the regulation of cardiomyocytes Ca2+ transportation.</p>

An observation of taurine transport alterations in calcification of myocardial cells in vitro / 中国医学科学院学报

<p><b>OBJECTIVE</b>To observe the alterations of taurine transport, taurine transporter (TAUT) and cysteine sulfinate decarboxylase (CSD) mRNA in the calcification of myocardial cells in vitro.</p><p><b>METHODS</b>3H-taurine measured the amount of taurine uptake. TAUT and CSD mRNA consents were measured using competitive quantitative RT-PCR in cultured and calcified myocardial cells.</p><p><b>RESULTS</b>In calcification of myocardial cells, taurine concentration was decreased by 27% (P < 0.05), taurine uptake was markedly reduced, Vmax reduced by 39% (P < 0.01), there were no statistical significance of Km values between the two groups. TAUT mRNA decreased by 45% (P < 0.01), but CSD mRNA increased by 25% (P < 0.05).</p><p><b>CONCLUSIONS</b>The data suggest that there were impediment of taurine transport in calcification of myocardial cells, as TAUT mRNA level was decreased, but CSD mRNA concentration was improved.</p>

Changes in adrenomedullin and receptor activity-modifying protein 2 mRNA in myocardium and vessels during L-NNA-induced hypertension in rats / 生理学报

To explore the changes in adrenomedullin (ADM) and receptor activity-modifying protein 2 (RAMP2) mRNA in myocardium and vessels in hypertension, a hypertensive rat model was prepared by administering L-NNA. Contents of ADM in plasma, myocardium and vessels were measured by radioimmunoassay (RIA). The levels of pro-ADM mRNA of myocardium and vessels were determined by competitive quantitative RT-PCR. The results showed that L-NNA induced hypertension and cardiomegaly. The ratio of heart to body weight increased by 35.5% (P<0.01). In hypertensive rats the ir-ADM in plasma, myocardium and vessels was increased by 80%, 72% and 57% (P<0.01), respectively compared with the control. The amounts of ADM mRNA in myocardium and vessels were increased by 50% and 109.2% (P<0.05), respectively, and the amounts of RAMP2 mRNA was increased by 132% and 87% (P<0.01), respectively, compared with control. The levels of ADM in myocardium and vessels were positively correlated with RAMP2 mRNA, the correlation coefficients were 0.741 and 0.885 (P<0.01), respectively. The results obtained indicate that in hypertensive rats, ADM is elevated in plasma, myocardium and ves-myocardium and vessel, and ADM and RAMP2 mRNA are up-regulated in myocardium and vessel. The ADM/RAMP2 system may play an important role in the pathogenesis of hypertension.

Dysfunction of myocardial and vascular taurine transport in spontaneously hypertensive rats / 生理学报

The alterations of taurine transport and the expression of taurine transporter (TAUT) mRNA in myocardium and aortic wall were investigated in spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. It was demonstrated that plasma taurine concentration and taurine release from myocardium and aortic wall in SHR were higher than those in WKY rats, whereas taurine content, taurine uptake and TAUT mRNA in myocardium and aortic wall of SHR were lower than those of WKY rats. In SHR, the maximal velocity (V(max)) of taurine transportation in myocardium and aortic wall was lower by 24% (P<0.05) and 35% (P<0.05) than that in WKY, their michaelis constants (Km) values were higher by 16% (P<0.05) and 39% (P<0.05), respectively. The results suggest that there is dysfunction of taurine transport in myocardium and aortic wall in SHR, which may be partly resulted from the decrease of TAUT activity and affinity, and down-regulation of TAUT gene expression.

Change in plasma ghrelin level and the relation between ghrelin and insulin resistance in type 2 diabetic patients after rosiglitazone therapy / 中华内分泌代谢杂志

The change in plasma ghrelin level after 4-and 12-week adjunctive therapy of rosiglitazones in type 2 diabetic patients inadequately controlled by sulphonylurea alone was observed and the relation between ghrelin and insulin resistance was analysed.The results showed that rosiglitazones significantly increased circulating ghrelin level and obviously decreased insulin resistance index after therapy for 4 and 12 weeks in type 2 diabetic patients.