EFFECTS OF OUABAIN AND DIGOXIN ON THE GENE EXPRESSION OFSODIUM PUMP α-SUBUNIT ISOFORM IN AORTIC SMOOTH MUSCLE OF RATS

Objective To compare the effects or ouabain and digoxin on both the systolic blood pressure and sodium pump a-subunit isoforms gene expression in the aortic smooth muscle of rats. Methods Normal Sprague- Dawley rats were injected with ouabain (20μg·kg-1·d-l,i. p), digoxin (32 μg·kg-1·d-1, i. p)and normal saline once a day, respectively, and indirect systolic blood pressure was recorded once a week. Six weeks later,all the rats were killed and sodium pump α1-,α2-,and α3-subunit mRNA levels were detected in the aortic smooth muscle with reverse transcription polymerase chain reaction（RT-PCR） method. Results The systolic blood pressure of rats infused with ouabain increased significantly at the end of week 6 [l32. 6±9.0 mmHg （1 mmHg = 0. 133 kPa） vs 115. 7 ± 8. 2 mmHg, P <0.01],while no difference of blood pressure was found between digoxin group and NS group （P>0.05）. The expression or sodium pump α-subunit isoforms in aortic smooth muscle was regulated by either ouabain or digox- in:both ouabain and digoxin increased α1- and α3-subunit expression, α2-subunit decreased in digoxin group but un- changed in ouabain group. Conclusion These results suggest that both ouabain and digoxin could regulate sodium pump α-subunit isoform expression, which might be related to the physiological roles or endogenous ouabain and might be responsible for the difference between the pharmacological and toxicological effects or ouabain and digoxin, including their effects on blood pressure.

Comparison of inositol phosphates formation and gene expression of Gq alpha subunit in cultured aortic smooth muscle cells from spontaneously hypertensive and Wistar Kyoto rats

Objecitve To explore whether phosphoinositide specific phospholipase C (PLC) activation via G protein in vascular smooth muscle cells (VSMCs) is altered in spontaneously hypertensive rats (SHR). Methods The VSMCs derived from aortae of SHR and Wistar Kyoto (WKY) rats were loaded for 48 hours with myo inositol. Inositol phosphate release was initiated by the addition of 10 5 mol/L norepinephrine in intact cells or by guanosine 5' 0 (3 thio tri sphosphate) (GTP gamma S) in permeabilized cells. In the meantime, growth arrested VSMCs were stimulated by 10% calf serum for 0, 30, 45, or 60 min, then gene expressions of Gq alpha subunit (G alph a q) were observed. Results There were no significant differences in inositol 1, 4,5 triphosphate (IP 3) level and expression of G alpha q mRNA between quiescent VSMCs from SHR and that from WKY. When stimulated by norepinephrine, IP 3 production increased transiently with a peak level at 10 s in VSMCs from WKY, and a rapid biphasic IP 3 response, which was significantly higher than that of WKY, in VSMCs from SHR had been observed. G proteins activated by GTP gamma S significantly raised IP 3 production in VSMCs from SHR compared to WKY (SHR vs WKY: 234.8%±29.2% vs 142.4%±12.0% of basal IP 3, P<0.05). In addition, the serum effect showed an significant increase in expression of G alpha q mRNA in VSMCs from SHR. Conclusions The hereditary factors are not the only variable regulating IP 3 metabolism and G alpha q gene expression. Influences of multi environmental factors such as vasoactive compounds, together with genetic predisposition, palys an important role in the highly sensitive response of IP 3 production and G alpha q gene over expression in SHR.

Up and Down Expression of Androgen Receptor, Estrogen Receptor beta and Platelet Derived Growth Factor beta by Testosterone in Aortic Vascular Smooth Muscle Tissues

Objectives To investigate the effects of testosterone enanthate (TE) on serum lip- ids and lipoproteins metabolism and the expression of androgen receptor (AR) , estrogen receptor beta ( ER - β) and platelet derived growth factor beta ( PDGFR - β) in aortic vascular smooth muscle tissues (VSMTs). Methods Forty aged male rats were ran- domly divided into 4 groups, group A (placebo group) , group B (2. 5 mg/kg intramuscular injection of TE once a week ) , group C (5.0 mg/kg intramuscular injection of TE once a week ) , group D ( 10. 0 mg/kg intramus- cular injection of TE once a week). All animals were fed freely during 16 - week treatment periods. The ex- pression of AR ,ER - βand PDGFR - β were studied by Western bolt. Results Average serum LDL - C was lower in group D than that in group A ( p < 0. 01 ). Compared with the other groups, average serum TC was also lower in group D (p <0. 05). AR expression in aortic vascular smooth muscle tissues could be regulated by TE: 99.50 ±21.74, 125.38 ±28.68 and 101.98 ± 15.42 for TE concentrations at 2.5 mg/kg, 5.0 mg/kg and 10.0 mg/kg, respectively , the expression of ER - β could be regulated by TE: 92. 34 ± 18. 68, 47. 72 ± 18.12, 82.13 ±23.50, and the expression of PDGFR - β could be regulated as well by TE: 219.70 ±45. 59, 50.16 ±9. 72, 125.36 ±15. 74(Data for AR ,ER-β and PDGFR - β protein band intensity were expressed with x ± s, with control group taken as 100 ).Conclusions This study indicates that androgens have significant effects on serum lipids and lipoprotein metabolism. Testosterone enanthate at 5. 0 mg/kg can stimulate the expression of AR, but inhibite the expres- sion of PDGFR. Testosterone enanthate at the concen- trations of 5. 0 mg/kg and 10. 0 mg/kg can inhibite the expression of ER - β.

Different effects of telmisartan and valsartan on human aortic vascular smooth muscle cell proliferation

Background Vascular smooth muscle cell proliferation is an important process in the development of atherosclerosis and is associated with other cellular processes in atherogenesis. Telmisartan is reported to have partial peroxisome proliferator-activated receptor （PPAR）-γ activating properties and has been referred to as selective PPAR modulators, but valsartan just blocks angiotensin II （Angll） type 1 （AT1） receptors. This study aimed to compare the different effects of telmisartan and valsartan on human aortic smooth muscle cells （HASMCs） proliferation. Methods Ability of telmisartan and valsartan to inhibit proliferation of HASMCs was evaluated by the Cell Counting Kit-8 （CCK-8） in continuous cell culture. Whether the antiproliferative effects of telmisartan and valsartan depend on their effects on Angll receptors or activating the peroxisome PPAR-y was also investigated in this study. Results Telmisartan inhibited proliferation of HASMCs by 52.4% （P 〈0.01） at the concentration of 25 μmol/L and the effect depended on the dose of telmisartan, but valsartan had little effect on HASMCs proliferation （P 〉0.05） and no dose response. When tested in cells stimulated with Angll, telmisartan had the same inhibition of HASMCs by 59.2% （P 〈0.05） and valsartan also inhibited it by 41.6% （P 〈0.05）. Telmisartan and valsartan had the same effect on down-regulating AT1 receptor expression and telmisartan was superior to valsartan up-regulating Angll type 2 （AT2） receptor expression. Antiproliferative effects of telmisartan were observed when HASMCs were treated with the PPAR-y antagonist GW9662 but antiproliferative effects of the PPAR-y activator pioglitazone were not observed. Conclusions Telmisartan, but not valsartan, inhibits HASMCs proliferation and has dose-dependent response without stimulation of Angll. AT2 receptor up-regulation of telmisartan contributes to its greater antiproliferative effects than valsartan. Its PPAR-y activation does not play a critical role in inhibiting HASMCs proliferation.