Atrial Ca²⁺ handling abnormalities, mainly involving the dysfunction of ryanodine receptor (RyR) and sarcoplasmic reticulum Ca²⁺-ATPase (SERCA), play a role in the pathogenesis of atrial fibrillation (AF). Previously, we found that the expression and function of transient receptor potential vanilloid subtype 4 (TRPV4) are upregulated in a sterile pericarditis (SP) rat model of AF, and oral administration of TRPV4 inhibitor GSK2193874 alleviates AF in this animal model. The aim of this study was to investigate whether oral administration of GSK2193874 could alleviate atrial Ca²⁺ handling abnormalities in SP rats. A SP rat model of AF was established by daubing sterile talcum powder on both atria of Sprague-Dawley (SD) rats after a pericardiotomy, to simulate the pathogenesis of postoperative atrial fibrillation (POAF). On the 3rd postoperative day, Ca²⁺ signals of atria were collected in isolated perfused hearts by optical mapping. Ca²⁺ transient duration (CaD), alternan, and the recovery properties of Ca²⁺ transient (CaT) were quantified and analyzed. GSK2193874 treatment reversed the abnormal prolongation of time to peak (determined mainly by RyR activity) and CaD (determined mainly by SERCA activity), as well as the regional heterogeneity of CaD in SP rats. Furthermore, GSK2193874 treatment relieved alternan in SP rats, and reduced its incidence of discordant alternan (DIS-ALT). More importantly, GSK2193874 treatment prevented the reduction of the S2/S1 CaT ratio (determined mainly by RyR refractoriness) in SP rats, and decreased its regional heterogeneity. Taken together, oral administration of TRPV4 inhibitor alleviates Ca²⁺ handling abnormalities in SP rats primarily by blocking the TRPV4-Ca²⁺-RyR pathway, and thus exerts therapeutic effect on POAF.
Administration, Oral ; Animals ; Atrial Fibrillation/etiology* ; Calcium/metabolism* ; Myocytes, Cardiac/metabolism* ; Pericarditis/pathology* ; Rats ; Rats, Sprague-Dawley ; Ryanodine Receptor Calcium Release Channel/pharmacology* ; Sarcoplasmic Reticulum/pathology* ; TRPV Cation Channels

OBJECTIVETo explore change of ryanodine receptor (RyR) in junior mouse with heart failure (HF) and the effect of β-adrenoreceptor blocker and Radix astragali on RyR in HF in this experiment.

METHODThe animal model of congestive heart failure was established by coarctation of abdominal aorta. Five weeks old mice were randomly divided into 4 groups: (1) HF group without treatment (n = 30); (2) HF group treated with carvedilol (n = 30); (3) HF group treated with carvedilol and Radix astragali(n = 30); (4) Sham-operated group (n = 30). Carvedilol and Radix astragali were administered through direct gastric gavage. After 4 weeks of treatment the high frequency ultrasound was performed. Myocardial sarcoplasmic reticulum (SR) was fractionated with ultra centrifugation. The time courses of Ca(2+) uptake and leak were determined by fluorescent spectrophotometry. The levels of expression of RyR2 in the 4 groups were detected by semi-quantitative reverse transcription-polymerase chain reaction.

RESULTCompared with the sham-operated group, left ventricular diastolic dimension (LVEDD) (P < 0.05), left ventricular systolic dimension (LVESD), interventricular septal thickness at end-diastole (IVSTd), interventricular septal thickness at end-systole (IVSTs), left ventricular posterior wall thickness at end-diastole (LVPWTd), and left ventricular posterior wall thickness at endsystole (LVPWTs) were all significantly increased (P < 0.01), ejection fraction (EF)(%) (HF group without treatment 51.60 ± 1.15, HF treated with carvedilol 72.06 ± 1.39, HF treated with carvedilol and Radix astragali 79.06 ± 1.09, sham-operated group 85.86 ± 1.45) and fractional shortening (FS) (HF group without treatment 44.55 ± 1.20, HF treated with carvedilol 44.55 ± 1.20, HF treated with carvedilol and Radix astragali 53.58 ± 1.30, sham-operated group 59.03 ± 1.67) were decreased (P < 0.01) in HF group without treatment. LVEDD (P < 0.05), LVESD, IVSTd, IVSTs, LVPWTd and LVPWTs were all significantly decreased (P < 0.01), EF and FS were increased (P < 0.01) in the cases with HF treated with carvedilol and carvedilol and Radix astragali when compared with HF group without treatment. EF and FS were much more increased in the group treated with carvedilol and Radix astragali than in those treated with carvedilol (P < 0.05). After adding thapsigargin to the buffer including SR of the four groups, there were fewer Ca(2+) leak (%) in sham-operated group (11.5 ± 4.3), HF group treated with carvedilol (15.6 ± 5.8) and treated with carvedilol and Radix astragali (13.6 ± 4.8) than that of HF group without treatment (65.6 ± 6.2) (P < 0.01), while after adding FK506 and thapsigargin together to the buffer including SR of four groups, there were marked Ca(2+) leak in sham-operated group (60.6 ± 7.8), HF group treated with carvedilol (66.2 ± 4.5)and those treated with carvedilol and Radix astragali (70.2 ± 5.5, P < 0.01). However, there was no additional increase in Ca(2+) leak in HF group (67.3 ± 7.5) compared with that of the group where only thapsigargin was added (P > 0.05). The levels of expression of RyR2 were significantly decreased in HF group and increased in the group treated with carvedilol and the group treated with carvedilol and Radix astragali.

CONCLUSIONThere was more cardiac Ca(2+) leak and the expression of RyR2 mRNA decreased in HF. Carvedilol and Radix astragali can increase expression of RyR2 mRNA and inhibit Ca(2+) leak by restoring the binding of FKBP12.6 back to RyR in HF to improve cardiac function and prevent left ventricle from remodeling.

Adrenergic beta-Antagonists ; pharmacology ; Animals ; Astragalus Plant ; Carbazoles ; pharmacology ; Drugs, Chinese Herbal ; pharmacology ; Heart Failure ; metabolism ; Male ; Propanolamines ; pharmacology ; Rats ; Rats, Wistar ; Ryanodine Receptor Calcium Release Channel ; drug effects ; metabolism

OBJECTIVETo study the expressions of ryanodine receptor 1 (RyR1) and voltage-gated calcium channel 1.3 (CaV1.3) in the corpus cavernosum smooth muscle of castrated rats and to investigate their role in androgen deficiency-related erectile dysfunction.

METHODSForty 8-week-old SD rats were equally randomized into Groups A (2-week sham-operation), B (4-week sham-operation), C (2-week castration), and D (4-week castration). After surgery, the levels of serum testosterone in different groups of rats were determined, and the expressions of RyR1 and CaV1.3 in the corpus cavernosum were detected by immunohistochemical staining and RT-PCR.

RESULTSThe levels of serum testosterone were significantly decreased in Groups C ([15.97 +/- 5.67] nmol/L) and D ([2.03 +/- 1.57] nmol/L) as compared with A ([90.54 +/- 20.13] nmol/L) and B ([120.35 +/- 30.32] nmol/L) (P < 0.05). RyR1 and CaV1.3 expressed in all the groups. RyR1 mRNA, CaV1.3 mRNA and their proteins were remarkably reduced in Groups C (0.51 +/- 0.24, 0.50 +/- 0.12, 120.36 +/- 25.78, 103.37 +/- 39.52, respectively) and D (0.33 +/- 0.15, 0.32 +/- 0.07, 67.39 +/- 30.54, 67.56 +/- 20.12, respectively) in comparison with A (1.53 +/- 0.25, 1.33 +/- 0.05, 300.96 +/- 135.12, 298.68 +/- 126.35, respectively) and B (1.37 +/- 0.23, 1.25 +/- 0.03, 330.38 +/- 128.59, 327.35 +/- 117.37, respectively) (P < 0.05). The androgen level was positively correlated with the expressions of RyR1 and CaV1.3.

CONCLUSIONAndrogen can regulate erectile function via RyR1 and CaV1.3.

Androgens ; pharmacology ; Animals ; Calcium Channels ; metabolism ; Male ; Muscle, Smooth ; drug effects ; metabolism ; Penis ; drug effects ; metabolism ; Rats ; Rats, Sprague-Dawley ; Ryanodine Receptor Calcium Release Channel ; metabolism

OBJECTIVETo study the effects of carvedilol combined with perindopril on Ca(2+) pump activity and the density of Ca(2+)-release channel ryanodine receptor (RyR2) in the myocardial sarcoplasmic reticulum (SR) in rats with chronic heart failure caused by myocardial infarction.

METHODSRat models of chronic heart failure established by left coronary artery ligation were divided into different groups and treated with carvedilol (6 mg.kg(-1).d(-1)), perindopril (4 mg.kg(-1).d(-1)), terazosin (2 mg.kg(-1).d(-1)), or the combination of carvedilol (6 mg.kg(-1).d(-1)) and perindopril (4 mg.kg(-1).d(-1)) for 9 weeks. Another 12 rats with sham operation served as the sham-operated group. The hemodynamic parameters, activity of SR Ca(2+) pump, and RyR2 density were determined.

RESULTSCompared with shame-operated group, the rats with chronic heart failure showed significantly increased left ventricular end-diastolic pressure (LVEDP) (P<0.01) and decreased +dP/dtmax, -dp/dtmax, activity of SR Ca(2+) pump and density of RyR2 (P<0.01). Both monotherapies with carvedilol and perindopril attenuated the increment of LVEDP, and significantly increased +dp/dtmax, -dp/dtmax, activity of SR Ca(2+) pump and density of RyR2 (P<0.01). Combined treatment even further enhanced the therapeutic effects, whereas terazosin produced no obvious effect. The activity of SR Ca(2+) pump was strongly correlated to +dp/dtmax and -dp/dtmax (r=0.596 and 0.684, respectively, P<0.01).

CONCLUSIONProlonged treatment with beta-blocker carvedilol in combination with ACE inhibitor perindopril may improve the hemodynamic parameters, enhance Ca(2+) pump activity and increase the density of RyR2 of myocardial SR more effectively than either monotherapy in preventing and treating chronic heart failure following myocardial infarction.

Animals ; Calcium ; metabolism ; Carbazoles ; pharmacology ; therapeutic use ; Drug Therapy, Combination ; Heart Failure ; drug therapy ; etiology ; metabolism ; Male ; Myocardial Infarction ; complications ; metabolism ; Perindopril ; pharmacology ; therapeutic use ; Propanolamines ; pharmacology ; therapeutic use ; Rats ; Rats, Wistar ; Ryanodine Receptor Calcium Release Channel ; drug effects ; Sarcoplasmic Reticulum ; drug effects ; metabolism

AIMTo investigate the vasodilating effect and its mechanism of ethanol on isolated rat thoracic aorta at different resting tension.

METHODSThe tension of the isolated Sprague-Dawley rat thoracic aorta rings perfused with different concentrations of ethanol was measured using organ bath technique.

RESULTSAt different resting tension (1.0, 1.5, 2.0, 2.5, 3.0, 3.5 and 4.0 g), ethanol (0.1-7.0 per thousand) caused a concentration-dependent relaxation on endothelium-denuded aortic rings precontracted with KCl (6 x 10(-2)mol/L) or phenylephrine (PE, 10(-6) mol/L), and the vasodilating effect was the most potent when the aortic rings were at the resting tension of 3 g. Ethanol had much less vasodilating effect on endothelium-intact aortic rings. Ethanol at 3 per thousand (the maximum-effect concentration) inhibited the CaCl2 induced contraction and downward shifted concentration-response curve of endothelium-denuded aortic rings pre-contracted with KCI or PE at the resting tension of 3 g. Incubation of aorta with ruthenium red (10(-5) mol/L) or heparin (50 mg/L) decreased the vasodilating effect of ethanol (3.0 per thousand) on endothelium-denuded aorta precontracted with PE at the resting tension of 3 g.

CONCLUSIONEthanol induces endothelium-independent relaxation on rat thoracic aorta, which is concerned with the resting tension. This effect of ethanol may be mediated by the inhibition of voltage-dependent and receptor-operated Ca2+ channels in the vascular smooth muscle cells. The inhibition of the ryanodine receptor and trisphosphate inositol (IP3) pathway may also contribute to this effect.

Animals ; Aorta, Thoracic ; drug effects ; Calcium Channel Blockers ; pharmacology ; Ethanol ; pharmacology ; In Vitro Techniques ; Inosine Triphosphate ; metabolism ; Male ; Muscle, Smooth, Vascular ; drug effects ; Rats ; Rats, Sprague-Dawley ; Ryanodine Receptor Calcium Release Channel ; drug effects ; Vasodilation ; drug effects

OBJECTIVESTo block the synthesis of ryanodine receptor 2 (RyR2) in myocardial cells by RNA interference and to investigate its biological impact on ischemia-reperfusion (I/R) in rat myocardial cells.

METHODSRat myocardial cells were isolated and cultured for an I/R model in vitro. RNA interference technique was used to block the synthesis of RyR2 in myocardial cells. Changes of LDH level, apoptosis, RyR2 mRNA expression and cytosolic Ca(2+) concentration were analyzed accordingly.

RESULTSMyocardial cells after I/R manipolation were severely injuried (LDH leakage, 125 IU/L vs 12 IU/L, P < 0.05), apoptosis (60.1% vs 5.5%, P < 0.05), significant cytosolic Ca(2+) overload (21.2 vs 7.6, P < 0.05) and remarkable mitochondrial membrane potential loss (37.2 vs 85.1, P < 0.05). However, no visible change of RyR2 was observed (20.1 vs 22.7, P > 0.05). Pre-treatment with RyR2 specified siRNA demonstrated suppressed expression of RyR2 (6.8 vs 20.1, P < 0.05), increased mitochondrial membrane potential (55.8 vs 37.2, P < 0.05), attenuated cytosolic Ca(2+) overload (8.6 vs 21.2) and cellular apoptosis (31.2% vs 60.1%, P < 0.05).

CONCLUSIONRyR2 gene silencing enables to protect myocardial cells from I/R injury in vitro.

Animals ; Apoptosis ; drug effects ; genetics ; Cells, Cultured ; Gene Silencing ; immunology ; physiology ; Membrane Potential, Mitochondrial ; drug effects ; immunology ; Myocardial Reperfusion Injury ; immunology ; pathology ; Myocytes, Cardiac ; drug effects ; pathology ; Oxygen ; metabolism ; RNA Interference ; RNA, Small Interfering ; pharmacology ; Rats ; Rats, Sprague-Dawley ; Reperfusion Injury ; immunology ; pathology ; Ryanodine Receptor Calcium Release Channel ; drug effects ; genetics

OBJECTIVETo investigate the vascular activity of extract from mulberry leaves (EML) on rat thoracic aorta and the underlying mechanism.

METHODSIsolated thoracic rings of Sprague-Dawley rats were mounted on the organ bath and the tension of the vessel was recorded.

RESULT(1) EML produced a concentration-dependent vasorelaxation of aorta preconstricted by high K(+) (60 mmol/L) or 10(-6) mol/L phenylephrine (PE) in endothelium-intact and endothelium-denuded arteries. (2) EML at EC(50) concentration reduced the calcium dose-response curve. (3) After incubation of aorta with verapamil, EML induced vasocontraction of aorta preconstricted by PE, which was abolished by ruthenium red.

CONCLUSIONThe vascular effect of EML is biphasic, the vasorelaxation is greater than the vasocontraction. The vasorelaxation induced by EML may be mediated by inhibition of voltage-and receptor-dependent calcium channels in vascular smooth muscle cells, while the vasocontraction is via activation of ryanodine receptor in endoplasmic reticulum.

Acetates ; isolation & purification ; pharmacology ; Animals ; Aorta, Thoracic ; drug effects ; physiology ; Dose-Response Relationship, Drug ; In Vitro Techniques ; Male ; Morus ; chemistry ; Plant Extracts ; isolation & purification ; pharmacology ; Plant Leaves ; chemistry ; Potassium ; pharmacology ; Rats ; Rats, Sprague-Dawley ; Ryanodine Receptor Calcium Release Channel ; physiology ; Vasoconstriction ; drug effects ; Vasodilation ; drug effects

Fatigue occurs when the interval of intermittent tetanic contraction of skeletal muscle is shortened to a certain degree and the contractile tension declines. After fatigue, prolongation of the contraction interval can make the contractile tension recover. In atrophic soleus, the recovery rate is slower. It has been shown that a decrease in the contractile tension is caused by the inhibition of the myofibrils and sarcoplasmic reticulum Ca(2+) release channels during fatigue. So the mechanism of the recovery of contractile tension is the recovery of the inhibited myofibrils and sarcoplasmic reticulum Ca(2+) release channels. But how the inhibition affects the recovery course is still unclear. To specify the factors modulating the recovery rate after intermittent tetanic fatigue in soleus, and to seek the reasons for the decrease in recovery rate in atrophic soleus, we observed the recovery time course of different types of fatigue in isolated soleus muscle strips. The 10% or 50% decrease in the maximal tetanic contractile tention (P(0)) was defined respectively as slight or moderate fatigue. After short-term (S10P, 10 s) and long-term (L10P, 300 s) slight fatigue, the tetanic contractile tension recovered to nearly 100% P(0) at the 20th minute. In both slight fatigue groups, perfusion with 10 mumol/L of ruthenium red (an inhibitor of Ca(2+) release channels in sarcoplasmic reticulum) slowed down the recovery rate. It was suggested that slight fatigue only induced inhibition of myofibrils. After short-term (S50P, 60 s) or long-term (L50P, 300 s) moderate fatigue, the tetanic contractile tension at the 20th minute recovered to about 95% P(0) in S50P group and 90% P(0) in L50P group, respectively. The recovery rate in L50P group was significantly lower than that in S50P group. So the recovery rate after moderate fatigue was related to the tetanic contraction duration. In both moderate fatigue groups, perfusion with 5 mmol/L of caffeine (an opener of Ca(2+) release channels in sarcoplasmic reticulum) resulted in nearly 100% recovery at the 5th minute. It was suggested that moderate fatigue induced inhibition of myofibrils and sarcoplasmic reticulum Ca(2+) release channels. In 1-week tail-suspended rats, soleus muscles showed a 40% of atrophy. After slight fatigue, the tetanic contractile tension in unloaded soleus recovered to 94% P(0) in S10P group and 95% P(0) in L10P. After moderate fatigue, the tetanic contractile tension in unloaded soleus recovered to 92% P(0) in S50P and 84% P(0) in L50P at the 20th minute. There were significant decreases in all of the fatigue groups as compared with the control groups. These results suggest that both slight and moderate fatigue inhibit the myofibrils and sarcoplasmic reticulum Ca(2+) release channels in 1-week unloaded soleus, so the recovery rate after tetanic fatigue is slower than that in the control group.
Animals ; Caffeine ; pharmacology ; Calcium ; metabolism ; Hindlimb Suspension ; Male ; Muscle Fatigue ; physiology ; Muscle, Skeletal ; pathology ; physiopathology ; Muscular Atrophy ; physiopathology ; Rats ; Rats, Sprague-Dawley ; Ruthenium Red ; pharmacology ; Ryanodine Receptor Calcium Release Channel ; physiology

OBJECTIVETo investigate the effects of 11, 12-epoxyeicosatrienoic acid (11, 12-EET) preconditioning and postconditioning on Ca(2+)-handling proteins in myocardial ischemia/reperfusion (IR) injury in rats and reveal the effects and mechanism of 11, 12-EET on cardioprotection. METHODS The IR injury model was built by stopping perfusion for 40 minutes followed by reperfusion for 30 minutes. The isolated Langendorff-perfused rat hearts were divided into 4 groups: control group, IR group, EET preconditioning (Pre-EET) group and EET postconditioning (Post-EET) group. The computer-based electrophysiological recorder system was used to measure the changes of the maximal rate of pressure increased in the contraction phase (+dp/dt(max)), the maximal rate of pressure decreased in the diastole phase (-dp/dt(max)), the left ventricular end diastolic pressure (LVEDP) and the difference of left ventricular pressure (delta LVP). The activity of Ca(2+)-ATPase in sarcoplasmic reticulum was measured with colorimetric method. Reverse transcription-polymerase chain reaction was used to assess the gene expression of C(a2+)-handling protein [sarcoplasic reticulum Ca(2+)-ATPase (SERCA), phospholamban (PLB), ryanodine receptor type 2 (RyR,), and 1, 4, 5-trisphosphate inositol receptor type 2 (IP3 R2) ] mRNAs level.

RESULTSCompared with IR group, the myocardial functions, the value of Ca(2+)-ATPase, and the expressions of IP3 R2 mRNA were significantly increased and the expression of PLB mRNA was significantly decreased in both Pre-EET group and Post-EET group (P < 0.05, P < 0.01). And the expression of SERCA mRNA was significantly increased in Pre-EET group (P < 0. 05). However, no significant differences were detected between Pre-EET and Post-EET groups. Moreover, the expression of RyR2 mRNA was not significantly different among all groups.

CONCLUSIONS11, 12-EET preconditioning and post-conditioning can protect myocardium from IR injury by elevating the activity of Ca(2+)-ATPase in sarcoplasmic reticulum, up-regulating the expression of IP3 R2 mRNA, and down-regulating the expression of PLB mRNA. Moreover, up-regulating the expression of SERCA mRNA maybe one of mechanisms of 11, 12-EET preconditioning on cardio protection against IR injury.

8,11,14-Eicosatrienoic Acid ; analogs & derivatives ; pharmacology ; Animals ; Calcium-Binding Proteins ; drug effects ; metabolism ; Inositol 1,4,5-Trisphosphate Receptors ; drug effects ; metabolism ; Ischemic Preconditioning, Myocardial ; methods ; Myocardial Reperfusion Injury ; metabolism ; prevention & control ; Rats ; Ryanodine Receptor Calcium Release Channel ; metabolism ; Sarcoplasmic Reticulum Calcium-Transporting ATPases ; drug effects ; metabolism

OBJECTIVETo investigate the effects of losartan on mRNA expression of myocardial sarcoplasmic reticulum calcium handling proteins (SERCA2, RyR2 and PLB) and the role of which in prevention of chronic heart failure in rabbit.

METHODSAfter chronic heart failure was induced by ligation of the left anterior descending artery in rabbits, the animals were treated with losartan. At 8 weeks after ligation, left ventricular function, hemodynamic parameters, and SERCA2, RyR2, PLB mRNA expressions were observed.

RESULTSCompared with the control group (group C), LVEDP in the infarcted group (group I) increased (P < 0.01), while +dp/dt(max) and -dp/dt(max) decreased significantly (P < 0.01). LVEDP was lower but +dp/dt(max) and -dp/dt(max) significantly higher in the losartan treated group (group L) than those in group I (P < 0.05). SERCA2, RyR2, and PLB mRNA expressions in group I were remarkably lower than those in group L (P < 0.01) and group C (P < 0.01), respectively.

CONCLUSIONLosartan can improve cardiac function, probably owing to its upregulating mRNA expressions of myocardial sarcoplasmic reticulum Ca(2+) handling proteins (RyR2, SERCA2 and PLB) in the prevention of heart failure.

Angiotensin II Type 1 Receptor Blockers ; pharmacology ; Animals ; Calcium ; metabolism ; Calcium Channels ; drug effects ; Calmodulin ; biosynthesis ; genetics ; Female ; Heart Failure ; drug therapy ; metabolism ; Losartan ; pharmacology ; Male ; Rabbits ; Ryanodine Receptor Calcium Release Channel ; biosynthesis ; Sarcoplasmic Reticulum ; drug effects ; metabolism