The impact of MicroRNA-155 on the effect of cryoablation in paroxysmal atrial fibrillation.

Elevated plasma MicroRNA-155 (miR-155) levels are strongly associated with cardiac fibrosis and chronic inflammation processes. However, the relationship between miR-155 and paroxysmal atrial fibrillation (PAF) recurrence following cryoablation remains poorly explored. We aimed to evaluate whether elevated miR-155 is related to long-term AF recurrence following cryoablation. Preoperative miR-155 levels were determined in PAF patients undergoing initial cryoablation. Multivariate-adjusted Cox models were constructed to determine the relationship between miR-155 levels and PAF recurrence. Multivariate logistic regression analyses were performed to determine predictors of PAF recurrence.  Of the 66 enrolled patients, 13 patients (19.7%) had recurrence at the 12-month following-up. These patients had significantly higher baseline miR-155 levels than those without PAF recurrence ((AAA ± BBB) vs. (AAA ± BBB), P < 0.05). The study results showed that miR-155 expression levels were significantly higher in the experimental group than in the control group. Additionally, logistic regression analysis revealed that miR-155 expression was positively correlated with PAF recurrence after cryoablation. Elevated preoperative miR-155 levels are related to a higher risk of AF recurrence and can independently predict AF recurrence following cryoablation.

Temporary pacemaker implantation via median cubital vein: A simple safe and effective technique.

BACKGROUND: Temporary cardiac pacemaker implantation (PM) via the femoral and subclavian veins is widely used in clinics to treat patients with severe bradycardia or tachycardia, but it is technically challenging and potentially associated with various complications. HYPOTHESIS: This study investigated the feasibility and safety of a novel method of PM implantation via the median cubital vein. METHODS: A total of 279 patients of the First Affiliated Hospital of Xiamen University between March 2020 and December 2021 who required no-emergency PM implantation were enrolled. The patients were divided into three groups based on the temporary PM implantation routes: F-control (n = 107), via the femoral vein; S-control (n = 67), via the subclavian vein, and N-group (n = 105), via the median cubital vein. The sheath placement time (SPT), electrode placement time (EPT), electrode arrival rate (EAR), rate of sensing and pacing (RSP), radiation quantity (RD), electrode dislocation rate (EDR) and average electrode retention time (AERT) were recorded and evaluated. In addition, the Hamilton Anxiety Scale (HAMA) and Self-Rating Depression Scale (SDS) were used to evaluate the comfort levels of patients in the three groups. RESULTS: There were no significant differences between the groups with regard to age, EAR, RSP, EPT, RD, and AERT (p > 0.05). However, the N-group had significantly lower SPT than the F-control and S-control groups (67.0 ± 22.0 s vs. 321.7 ± 122.2 s and 307.3 ± 128.5 s, p = 0.000). Additionally, the F-control had significantly higher EDR than the S-control group and the N-group (11 (10.3%) vs. 2 (3.0%) and 3 (2.9%), p = 0.036). Besides, comparison of the HAMA and SDS scores before and after PM implantation showed significant differences in the S-control group (p = 0.010) and the N-group (p = 0.000). CONCLUSIONS: Temporary PM implantation via the median cubital vein is safe, effective, and less time-consuming.

A new risk score for the assessment of outcomes for Chinese patients with peripartum cardiomyopathy.

BACKGROUND: Peripartum cardiomyopathy (PPCM) is a potentially life-threatening complication of pregnancy, but identifying patients at higher risk of this condition remains difficult. OBJECTIVES: We conducted a study to identify new risk factors associated with PPCM and predictors of poor outcomes. METHODS: This retrospective analysis included a total of 44 women with PPCM. As a control group, 79 women who gave birth around the same time as the PPCM patients and who did not have organic disease were included. A multivariate regression analysis was conducted to identify risk factors associated with PPCM and with delayed recovery. RESULTS: All PPCM patients were discharged within 28 days. In comparison to the control group, PPCM patients had higher rates of preeclampsia (20.4% vs. 1.27%, P<0.001), autoimmune disease (27.3% vs. 11.4%, P = 0.018), and cesarean delivery with preterm labor (31.8% vs. 17.7%, P = 0.037). The neonates of PPCM patients had lower birth weight (2.70±0.66 kg vs. 3.21±0.57 kg, P<0.001). PPCM patients had higher levels of C-reactive protein, d-dimer, brain natriuretic peptide (BNP), and serum phosphorus, but lower levels of albumin and serum calcium (all P<0.001). In all patients with PPCM, the left ventricular ejection fraction (LVEF) returned to normal (≥50%) within 28 days after admission. Subjects with early recovery (n = 34) had lower BNP than those with delayed recovery (n = 10) (649.7 ± 526.0 pg/mL vs. 1444.1 ± 1040.8 pg/mL, P = 0.002). Multivariate regression led to a three-point score system to predict PPCM (1 point each for the presence of pericardial effusion, left ventricular dilatation, and d-dimer level ≥0.5 µg/mL). At a cutoff of ≥2, this scoring system predicted delayed recovery with 95.5% sensitivity and 96.1% specificity. The negative predictive value was 97.4% and the positive predictive value was 93.3%. Binary logistic regression indicated that PPCM patients with pulmonary hypertension, lower hemoglobin, or worse LVEF tended to require longer hospital stay (minimum 14 days). CONCLUSIONS: A risk score that consists of pericardial effusion, left ventricular dilatation, and d-dimer level ≥ 0.5 µg/mL could help streamline the diagnosis of PPCM prior to confirmatory investigations. Moreover, a risk score that consists of pulmonary hypertension, lower hemoglobin and worse LVEF could help to predict poor outcomes in PPCM patients.

Corrigendum: Artemisinin relieves myocardial ischemia-reperfusion injury via modulating miR-29b-3p and hemicentin 1.

[This corrects the article DOI: 10.3389/fphar.2022.918966.].

Acute Coronary Syndrome May be Associated with Decreased Resolvin D1-to-Leukotriene B4 Ratio.

An imbalance between inflammation-resolving lipid mediators and proinflammatory leukotrienes with the instability of atherosclerotic plaques in experimental models has been reported. However, the contribution of the balance of Resolvin D1 (RvD1) to Leukotriene B4 (LTB4) in predicting acute coronary syndrome (ACS) remains unknown. This study investigated the association of RvD1-to-LTB4 ratio with ACS.Eighty-one patients with ACS and 90 stable coronary artery disease (SCAD) patients were included in this study. Plasma RvD1 and LTB4 levels were measured with commercial kits.Patients with ACS had higher LTB4 levels, lower RvD1 levels, and a lower RvD1-to-LTB4 ratio than patients with SCAD. History of diabetes mellitus, elevated Troponin I, LTB4, and decreased RvD1-to-LTB4 ratio (odds ratio [OR]: 1.025; 95% confidence interval [CI]: 1.014-1.040; P < 0.001) were independently correlated with ACS. Receiver operating characteristic curve analysis demonstrated that RvD1-to-LTB4 ratio was a potential biomarker for the risk of ACS.A circulating proinflammatory lipid profile, characterized by a low RvD1-to-LTB4 ratio may be associated with ACS in patients with ischemic heart disease.

SRC-3 deficiency prevents atherosclerosis development by decreasing endothelial ICAM-1 expression to attenuate macrophage recruitment.

Steroid receptor coactivator 3 (SRC-3) is a member of the p160 SRC family. This factor can interact with multiple nuclear hormone receptors and transcription factors to regulate the expression of their target genes. Although many physiological roles of SRC-3 have been revealed, its role in atherosclerosis is not clear. In this study, we found that SRC-3-/-ApoE-/- mice have reduced atherosclerotic lesions and necrotic areas in their aortas and aortic roots compared with SRC-3+/+ApoE-/- mice after Western diet (WD) feeding for 12 weeks. RNA-Seq and Western blot analyses of the aorta revealed that SRC-3 was required for maintaining the expression of ICAM-1, which was required for macrophage recruitment and atherosclerosis development. siRNA-mediated knockdown of SRC-3 in endothelial cells significantly reduced WD-induced atherosclerotic plaque formation. Additionally, treatment of ApoE-/- mice with SRC-3 inhibitor bufalin prevented atherosclerotic plaque development. SRC-3 deficiency reduced aortic macrophage recruitment. Accordingly, ICAM-1 expression was markedly decreased in the aortas of SRC-3-/-ApoE-/- mice and ApoE-/- mice with endothelial SRC-3 knockdown mediated by AAV9-shSRC-3 virus. Mechanistically, SRC-3 coactivated NF-κB p65 to increase ICAM-1 transcription in endothelial cells. Collectively, these findings demonstrate that inhibiting SRC-3 ameliorates atherosclerosis development, at least in part through suppressing endothelial activation by decreasing endothelial ICAM-1 expression via reducing NF-κB signaling.

Artemisinin relieves myocardial ischemia-reperfusion injury via modulating miR-29b-3p and hemicentin 1.

Objective: To explore the impact of artemisinin (ARS) on myocardial ischemia-reperfusion (I/R) injury and the underlying mechanism. Methods: Myocardial I/R rat model and cell model were used in this study. The cell viability, morphological changes, apoptosis, and oxidative stress were evaluated in cardiomyocytes H9c2 cells in vitro by using cell counting kit-8, microscope, flow cytometry, and commercial kits. High throughput sequencing is used to identify molecular targets of ARS on myocardial I/R injury, and then the gene-gene interaction network was constructed. MiR-29b-3p, hemicentin 1 (HMCN1), and apoptosis-related genes were tested by qRT-PCR and Western blotting. In the myocardial I/R rat model, echocardiography, (Triphenyl tetrazolium chloride) TTC staining, Hematoxylin-eosin (H&E) staining, Masson Trichrome staining, and TUNEL staining are applied to evaluate the protective effect of ARS on the myocardial injury. Results: In vitro, we demonstrated that ARS alleviated H2O2-induced myocardial I/R injury, manifested by increased H9c2 viability, decreased pathological changes, apoptosis, and oxidative stress biomarker ROS, LDH, and CK-MB. Then, sequencing analysis revealed that miR-29b-3p/HMCN1 was the target of ARS for myocardial I/R injury. Notably, rescue experiments indicated that ARS inhibited myocardial I/R injury through targeted regulation miR-29b-3p/HMCN1. In vivo, we confirmed that ARS reduced myocardial injury, fibrosis, and apoptosis via modulation of miR-29b-3p/HMCN1. Conclusion: This study demonstrated the functional role of the ARS/miR-29b-3p/HMCN1 axis in alleviating myocardial I/R injury, which provided a new direction for myocardial I/R injury therapy.

Inhibition of GSDMD Activates Poly(ADP-ribosyl)ation and Promotes Myocardial Ischemia-Reperfusion Injury.

The precise control of cardiomyocyte viability is imperative to combat myocardial ischemia-reperfusion injury (I/R), in which apoptosis and pyroptosis putatively contribute to the process. Recent researches indicated that GSDMD is involved in I/R as an executive protein of pyroptosis. However, its effect on other forms of cell death is unclear. We identified that GSDMD and GSDMD-N levels were significantly upregulated in the I/R myocardium of mice. Knockout of GSDMD conferred the resistance of the hearts to reperfusion injury in the acute phase of I/R but aggravated reperfusion injury in the chronic phase of I/R. Mechanistically, GSDMD deficiency induced the activation of PARylation and the consumption of NAD+ and ATP, leading to cardiomyocyte apoptosis. Moreover, PJ34, a putative PARP-1 inhibitor, reduced the myocardial injury caused by GSDMD deficiency. Our results reveal a novel action modality of GSDMD in the regulation of cardiomyocyte death; inhibition of GSDMD activates PARylation, suggesting the multidirectional role of GSDMD in I/R and providing a new theory for clinical treatment.

An improved procedure for isolating adult mouse cardiomyocytes for epicardial activation mapping.

Cardiovascular disease is a leading cause of death and disability worldwide. Although genetically modified mouse models offer great potential for robust research in vivo, in vitro studies using isolated cardiomyocytes also provide an important approach for investigating the mechanisms underlying cardiovascular disease pathogenesis and drug actions. Currently, isolation of mouse adult cardiomyocytes often relies on aortic retrograde intubation under a stereoscopic microscope, which poses considerable technical barriers and requires extensive training. Although a simplified, Langendorff-free method has been used to isolate viable cardiomyocytes from the adult mouse heart, the system requires enzymatic digestions and continuous manual technical operation. This study established an optimized approach that allows isolation of adult mouse cardiomyocytes and epicardial activation mapping of mouse hearts using a Langendorff device. We used retrograde puncture through the abdominal aorta in vivo and enzymatic digestion on the Langendorff perfusion device to isolate adult mouse cardiomyocytes without using a microscope. The yields of isolated cardiomyocytes were amenable to patch clamp techniques. Furthermore, this approach allowed epicardial activation mapping. We used a novel, simplified method to isolate viable cardiomyocytes from adult mouse hearts and to map epicardial activation. This novel approach could be beneficial in more extensive research in the cardiac field.

Genetic Characteristics and Transcriptional Regulation of Sodium Channel Related Genes in Chinese Patients With Brugada Syndrome.

Objective: To investigate the genetic characteristics and transcriptional regulation of the SCN5A gene of Brugada syndrome (BrS) patients in China. Methods: Using PubMed, Medline, China National Knowledge Internet (CNKI), and Wanfang Database, Chinese patients with BrS who underwent SCN5A gene testing were studied. Results: A total of 27 suitable studies involving Chinese BrS patients who underwent the SCN5A gene test were included. A total of 55 SCN5A gene mutations/variations were reported in Chinese BrS patients, including 10 from southern China and 45 from northern China. Mutations/variations of BrS patients from southern China mostly occurred in the regions of the α-subunit of Nav1.5, including DIII (Domain III), DIV, DIII-DIV, C-terminus regions, and the 3'UTR region. Furthermore, we analyzed the post-transcriptional modifications (PTMs) throughout the Nav1.5 protein encoded by SCN5A and found that the PTM changes happened in 72.7% of BrS patients from southern China and 26.7% from northern China. Conclusions: SCN5A mutations/variations of BrS patients in southern China mostly occurred in the DIII-DIV to C-terminus region and the 3'-UTR region of the SCN5A gene, different from northern China. PTM changes were consistent with the mutation/variation distribution of SCN5A, which might be involved in the regulation of the pathogenesis of BrS patients.

Inhibited HDAC3 or Elevated MicroRNA-494-3p Plays a Protective Role in Myocardial Ischemia-Reperfusion Injury via Suppression of BRD4.

Increased histone deacetylase 3 (HDAC3) has been demonstrated to contribute to the pathogenesis of myocardial ischemia-reperfusion injury (MI/RI). Therefore, the goal of this study was to investigate how HDAC3 regulated MI/RI by mediating microRNA (miR)-494-3p/dromodomain-containing protein 4 (BRD4) axis. The MI/RI model was established by ligating the right anterior descending coronary artery. Cardiomyocytes from newborn mice were treated with hypoxia/reoxygenation (H/R). Gain-of-function and loss-of-function approaches were implemented to figure out the roles of miR-494-3p and HDAC3 in MI/RI. miR-494-3p, HDAC3, and BRD4 in myocardial tissues of mice with MI/RI and H/R-treated cardiomyocytes were detected. The relationships between miR-494-3p and HDAC3 and BRD4 were identified. Reduced miR-494-3p and upregulated HDAC3 and BRD4 exhibited in myocardial tissues of mice with MI/RI and H/R-treated cardiomyocytes. Inhibited HDAC3 or elevated miR-494-3p repressed the inflammation and apoptosis, improved cardiac function, and ameliorated myocardial injury in myocardial tissues of mice with MI/RI. Suppression of HDAC3 or elevation of miR-494-3p depressed inflammation and apoptosis and promoted cell viability of primary cardiomyocytes. miR-494-3p targeted BRD4. The study concludes that suppressed HDAC3 plays a protective role in MI/RI by upregulation of miR-494-3p and inhibition of BRD4, which could be helpful for MI/RI therapy.

miR-190a-5p Partially Represses the Abnormal Electrical Activity of SCN3B in Cardiac Arrhythmias by Downregulation of IL-2.

Cardiac arrhythmias (CAs) are generally caused by disruption of the cardiac conduction system; interleukin-2 (IL-2) is a key player in the pathological process of CAs. This study aimed to investigate the molecular mechanism underlying the regulation of IL-2 and the sodium channel current of sodium voltage-gated channel beta subunit 3 (SCN3B) by miR-190a-5p in the progression of CAs. ELISA results suggested the concentration of peripheral blood serum IL-2 in patients with atrial fibrillation (AF) to be increased compared to that in normal controls; fluorescence in situ hybridization indicated that the expression of IL-2 in the cardiac tissues of patients with AF to be upregulated and that miR-190a-5p to be downregulated. Luciferase reporter assay, quantitative real-time-PCR, and whole-cell patch-clamp experiments confirmed the downregulation of IL-2 by miR-190a-5p and influence of the latter on the sodium current of SCN3B. Overall, miR-190a-5p suppressed the increase in SCN3B sodium current caused by endogenous IL-2, whereas miR-190a-5p inhibitor significantly reversed this effect. IL-2 was demonstrated to be directly regulated by miR-190a-5p. We, therefore, concluded that the miR-190a-5p/IL-2/SCN3B pathway could be involved in the pathogenesis of CAs and miR-190a-5p might acts as a potential protective factor in pathogenesis of CAs.

No association between tumor laterality and cardiac-related mortality in breast cancer patients after radiotherapy: a population-based study.

INTRODUCTION: To assess the effect of tumor laterality to cardiac-related deaths of breast cancer in the current radiation practices using a large modern population-based study. METHODS: Women diagnosed with breast cancer from 2000 to 2008 were included using the current Surveillance, Epidemiology, and End Results database. The primary outcome of this study was the cardiac-related mortality. Multivariate analysis was performed using the Cox proportional hazards model to analyze the cardiac-related mortality including demographic, clinicopathologic, and treatment factors. RESULTS: We identified 168,761 breast cancer patients, including 85,006 (50.4%) patients with left-sided tumors and 83,755 (49.6%) patients with right-sided tumors. The median follow-up period was 8.8 years. The 10-year cardiac-related mortality was 2.3% and 2.3% in left- and right-sided tumors, respectively (P=0.685). The results indicated that patients with older age, non-Hispanic Black, receipt of mastectomy, and married status were the independent adverse factors for cardiac-related mortality. However, left-sided tumors were not associated to a higher risk of cardiac-related mortality than right-sided tumors following postoperative radiotherapy (right vs left, hazard ratios 1.025, 95% CI 0.856-1.099, P=0.484). The risk of cardiac-related mortality in the entire cohort was increased with the extension of follow-up time. However, there was still not significantly different between left- and right-sided tumors. Subgroup analysis also found no association between tumor laterality and cardiac-related mortality after postoperative radiotherapy based on various demographics and treatment factors. CONCLUSION: With a median follow-up of 8.8 years, no significant differences were found in cardiac-related mortality between left- and right-sided tumors under current radiation practices of breast cancer patients.

Genomic Profiling of Adult and Pediatric B-cell Acute Lymphoblastic Leukemia.

Genomic landscapes of 92 adult and 111 pediatric patients with B-cell acute lymphoblastic leukemia (B-ALL) were investigated using next-generation sequencing and copy number alteration analysis. Recurrent gene mutations and fusions were tested in an additional 87 adult and 93 pediatric patients. Among the 29 newly identified in-frame gene fusions, those involving MEF2D and ZNF384 were clinically relevant and were demonstrated to perturb B-cell differentiation, with EP300-ZNF384 inducing leukemia in mice. Eight gene expression subgroups associated with characteristic genetic abnormalities were identified, including leukemia with MEF2D and ZNF384 fusions in two distinct clusters. In subgroup G4 which was characterized by ERG deletion, DUX4-IGH fusion was detected in most cases. This comprehensive dataset allowed us to compare the features of molecular pathogenesis between adult and pediatric B-ALL and to identify signatures possibly related to the inferior outcome of adults to that of children. We found that, besides the known discrepancies in frequencies of prognostic markers, adult patients had more cooperative mutations and greater enrichment for alterations of epigenetic modifiers and genes linked to B-cell development, suggesting difference in the target cells of transformation between adult and pediatric patients and may explain in part the disparity in their responses to treatment.

Exome sequencing identifies somatic mutations of DDX3X in natural killer/T-cell lymphoma.

Natural killer/T-cell lymphoma (NKTCL) is a malignant proliferation of CD56(+) and cytoCD3(+) lymphocytes with aggressive clinical course, which is prevalent in Asian and South American populations. The molecular pathogenesis of NKTCL has largely remained elusive. We identified somatic gene mutations in 25 people with NKTCL by whole-exome sequencing and confirmed them in an extended validation group of 80 people by targeted sequencing. Recurrent mutations were most frequently located in the RNA helicase gene DDX3X (21/105 subjects, 20.0%), tumor suppressors (TP53 and MGA), JAK-STAT-pathway molecules (STAT3 and STAT5B) and epigenetic modifiers (MLL2, ARID1A, EP300 and ASXL3). As compared to wild-type protein, DDX3X mutants exhibited decreased RNA-unwinding activity, loss of suppressive effects on cell-cycle progression in NK cells and transcriptional activation of NF-κB and MAPK pathways. Clinically, patients with DDX3X mutations presented a poor prognosis. Our work thus contributes to the understanding of the disease mechanism of NKTCL.

Electrophysiological characteristics of a SCN5A voltage sensors mutation R1629Q associated with Brugada syndrome.

Brugada syndrome (BrS) is an inherited arrhythmogenic syndrome leading to sudden cardiac death, partially associated with autosomal dominant mutations in SCN5A, which encodes the cardiac sodium channel alpha-subunit (Nav1.5). To date some SCN5A mutations related with BrS have been identified in voltage sensor of Nav1.5. Here, we describe a dominant missense mutation (R1629Q) localized in the fourth segment of domain IV region (DIV-S4) in a Chinese Han family. The mutation was identified by direct sequencing of SCN5A from the proband's DNA. Co-expression of Wild-type (WT) or R1629Q Nav1.5 channel and hß1 subunit were achieved in human embryonic kidney cells by transient transfection. Sodium currents were recorded using whole cell patch-clamp protocols. No significant changes between WT and R1629Q currents were observed in current density or steady-state activation. However, hyperpolarized shift of steady-state inactivation curve was identified in cells expressing R1629Q channel (WT: V1/2 = -81.1 ± 1.3 mV, n = 13; R1629Q: V1/2 = -101.7 ± 1.2 mV, n = 18). Moreover, R1629Q channel showed enhanced intermediate inactivation and prolonged recovery time from inactivation. In summary, this study reveals that R1629Q mutation causes a distinct loss-of-function of the channel due to alter its electrophysiological characteristics, and facilitates our understanding of biophysical mechanisms of BrS.

Identification of autotoxic compounds in fibrous roots of Rehmannia (Rehmannia glutinosa Libosch.).

Rehmannia is a medicinal plant in China. Autotoxicity has been reported to be one of the major problems hindering the consecutive monoculture of Rehmannia. However, potential autotoxins produced by the fibrous roots are less known. In this study, the autotoxicity of these fibrous roots was investigated. Four groups of autotoxic compounds from the aqueous extracts of the fibrous roots were isolated and characterized. The ethyl acetate extracts of these water-soluble compounds were further analyzed and separated into five fractions. Among them, the most autotoxic fraction (Fr 3) was subjected to GC/MS analysis, resulting in 32 identified compounds. Based on literature, nine compounds were selected for testing their autotoxic effects on radicle growth. Seven out of the nine compounds were phenolic, which significantly reduced radicle growth in a concentration-dependent manner. The other two were aliphatic compounds that showed a moderate inhibition effect at three concentrations. Concentration of these compounds in soil samples was determined by HPLC. Furthermore, the autotoxic compounds were also found in the top soil of the commercially cultivated Rehmannia fields. It appears that a close link exists between the autotoxic effects on the seedlings and the compounds extracted from fibrous roots of Rehmannia.

Effect of didrovaltrate on I-calcium current in rabbit ventricular myocytes.

OBJECTIVE: To investigate the effect of didrovaltrate on L-type calcium current (I(Ca-L)) in rabbit ventricular myocytes. METHODS: We used the whole cell patch clamp recording technique. RESULTS: Didrovaltrate at concentrations of 30 microg/ L and 100 microg/L significantly decreased peak I(Ca-L) (I(Ca-Lmax)) from (6.01 +/- 0.48) pA/pF to (3.45 +/- 0.27) pA/pF and (2.16 +/- 0.19) pA/pF (42.6% and 64.1%, n=8, P< 0.01), respectively. Didrovaltrate shifted upwards the current-voltage curves of I(Ca-L) without changing their active, peak and reverse potentials. Didrovaltrate affected the steady-state inactivation of I(Ca-L). The half activation potential (V1/2) was significantly shifted from (-26 +/- 2) to (-36 +/- 3) mV (n=6, P<0.05), with a significant change in the slope factor (k) (from 8.8 +/- 0.8 to 11.1 +/- 0.9, n=6, P<0.05). Didrovaltrate did not affect the activation curve. CONCLUSION: Didrovaltrate blocks I(Ca-L) in a concentration-dependent manner and probably inhibits I(Ca-L) in its inactive state, which may contribute to its cardiovascular effect.