Exercise unmasks impaired vascular and cardiac hemodynamic in patients with hypertrophic cardiomyopathy

Background/Introduction

Exertional dyspnea is a common finding in patients with Hypertrophic Cardiomyopathy (HCM), yet little data is available regarding the hemodynamic disturbances that lead to symptom development in this population.

Purpose

To investigate the mechanisms involved in the functional limitation of patients with HCM.

Methods

We prospectively studied 20 symptomatic patients with confirmed diagnosis of HCM. Assessment included NT-pro BNP levels, echocardiogram, and invasive characterization, where subjects also underwent invasive cardiopulmonary exercise testing.

Results

Median patient age was 57 (48–66) years old and 15 (75%) were male. Basal NT-pro BNP was elevated (748 pg/mL [406–1082]) and 8 (40%) subjects had NYHA functional Class III despite optimal medical treatment. Sarcomeric abnormal mutations were identified in 12 subjects (60%), most frequently in MYBPC3. Ultrasound imaging showed marked left ventricle (LV) hypertrophy (LV Mass Index 140 g/m2 [109–161]), with signs of LV outflow obstruction in 13 (65%) subjects. All patients displayed preserved ejection fraction (68% [61–73]). Significant mitral regurgitation was present in 5 subjects and median E/e' was 9.87 [6.43–13.14].

At rest, biventricular filling pressures were relatively normal, with upper limit mean Pulmonary Pressure (Table). Patients exercised for 6.4 (95% CI: 5.6–7.2) min, achieving a respiratory exchange ratio of 1.11 (1.02–1.17). All subjects displayed normal cardiac output at rest (5.6 L/min (3.7–7.5)), that increased during exertion, due mostly to a rise in heart rate (p<0.0001). Exercise doubled LV End-Diastolic Pressure from 15.3 (11.5–19.1) mmHg at baseline to 30.4 (26.6–34.3) mmHg at peak VO2 (p<0.0001), whereas mean pulmonary pressure increased from 21 (14–29) mmHg to 40 (33–47) mmHg (p<0.0001).

Remarkably, although arterial hemodynamics were relatively normal at baseline, exercise induced significant increases both in the continuous (systemic vascular resistance) and pulsatile components of vascular load (Impedances, p<0.05; Table 1) (Figure 1). This increase in afterload during exertion has not been previously documented in HCM. The decreased compliance derived, can also play a role in the elevated filling pressures documented on exertion.

Conclusion

Exercise unmasks adverse hemodynamics in HCM, severely increasing LV filling pressures and showing systemic arterial dysfunction.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Instituto de Salud Carlos III, Spain.

Cohort of patients with hypertrophic cardiomyopathy and alpha tropomyosin 1 variants followed up at a national reference center

Background

Hypertrophic cardiomyopathy (HCM), the most common inherited cardiac condition, is mainly caused by pathogenic variants in sarcomeric genes. Alpha tropomyosin gene (TPM1) account for a small percentage (1–5%) of HCM cases with ∼20 relevant variants described so far related to this condition. However, TPM1–hypertrophic cardiomyopathy is thought to be associated with high rates of heart failure and sudden death (SD).

Purpose

To describe the phenotype and genotype of a cohort of adult and pediatric patients with HCM and variants in TPM1 followed up in an inherited cardiovascular disease program of a national reference center.

Methods

Patients with HCM and TPM1 variants potentially related to the phenotype were retrospectively identified. Genetic test was performed by next generation sequencing panels or clinical exome. Clinical data, any need of intervention (obstruction relief, device implantation, heart transplant) and major adverse cardiovascular events were collected from medical records. We performed co-segregation studies whenever possible. Predictive models in order to support the possible pathogenicity of the variants were also applied.

Results

We identified 13 individuals (54% females) from 11 families with HCM and variants in TPM1. 12 patients had phenotype and one was a carrier. 5 out of 12 patients (42%) were diagnosed before the age of 12 years, all with severe phenotype. The most frequent pattern was asymmetric septal hypertrophy, with a mean thickness of the septum of 22 mm (range 14–37). 4 cases were obstructive, of which 3 required surgical myectomy. 4 patients required an implanted cardiac defibrillator (ICD), all in childhood. One was in secondary prevention after an aborted SD in a 12-year-old girl. 3 appropriate therapies were recorded in 2 patients during follow-up. A girl underwent heart transplantation at the age of 12 because of angina at rest. At last evaluation 67% were symptomatic, with 3 patients in functional class II and 5 patients in functional class III-IV/IV.

8 missense variants in TPM1 were identified in the 11 families (table 1). All variants are described in Clinvar as variants of unknown significance (VUS). They appear at a very low frequency (<0.01%) or are absent in general population and predictive models of protein structure and functionality (PreditProtein) indicate an impact on the structure of the protein, supporting their possible pathogenicity. Figure 1 shows a diagram of the variants position within TPM1 gen. Cossegregation data and the presence of the same variant in non_related families allowed us to reclassify 4 variants as “likely pathogenic”.

Conclusion

This study provides cosegregation data and “in silico” analysis of the potential functional impact of several TPM1 variants, supporting their pathogenicity. In our cohort, HCM related to TMP1 variants is associated with high penetrance (92%), early onset and poor clinical course in childhood and youth.

Funding Acknowledgement

Type of funding sources: None. Figure 1

Extracellular vesicles secreted by human cardiosphere-derived cells attenuate electrophysiological remodelling in an in vitro model of atrial fibrillation

Background

Stem cells and their secreted extracellular vesicles (EVs) have shown different cardioprotective effects. However, their impact on the electrophysiological properties of the heart tissue remains controversial. While the use of some progenitor cells seems to have antiarrhythmic potential, the use of cardiomyocyte-like cells may be proarrhythmic. The mechanisms behind, and whether these effects are linked to cell engraftment and not to their secreted products is not fully known.

Purpose

The aim of this study was to investigate the electrophysiological modifications induced by extracellular vesicles secreted by human cardiosphere-derived cells (CDC-EVs) in an in vitro model of atrial fibrillation in order to explore their potential antiarrhythmic effect.

Methods

CDCs were derived from cardiac biopsies of patients who underwent cardiac surgery for other reasons. Purified CDC-EVs resuspended in serum-free media (SFM) vs. SFM alone were added to HL-1 atrial myocyte monolayers presenting spontaneous fibrillatory activity. After 48 hours, the monolayers were fully confluent, and the electrophysiological properties were analysed through optical mapping in both the treated (n=9) and control plates (n=9). Optical mapping recordings of the monolayers were analysed with Matlab for the activation frequency, activation complexity, rotor dynamics (curvature and meandering) and conduction velocity.

Results

CDC-EVs reduced activation complexity of the fibrillating atrial monolayers by ∼40% (2.74±0.59 vs. 1.61±0.16 PS/cm2, p<0.01). This reduction in activation complexity was accompanied by larger rotor meandering (1.47±0.82 vs. 4.32±2.25 cm/s, p<0.01) and decreased curvature (1.79±0.40 vs. 0.87±0.24 rad/cm, p<0.01) in the treated group. Despite reduction in the activation complexity, activation frequency did not change significantly between both groups. This could be in part because CDC-EVs increased conduction velocity by 80% (1.32±0.57 vs. 2.65±0.87 cm/s, p<0.01). Low conduction velocity has been linked to higher reentry recurrence, and lower meandering and higher curvature to higher rotor stability and harder AF termination. Therefore, CDC-EVs seem to drive cardiomyocytes to a less arrhythmic profile reducing activation complexity and preventing remodelling by increasing conduction velocity and modifying rotor dynamics.

Conclusions

CDC-EVs significantly modify conduction velocity and rotor dynamics, therefore reducing fibrillation complexity and remodelling to drive atrial myocytes to a less arrhythmogenic profile. Testing CDC-EVs in more robust models of atrial fibrillation, the most common sustained arrhythmia in humans with significant morbidity and mortality, is of special interest.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Instituto de Salud Carlos III, Ministerio de Ciencia e Innovaciόn,CIBERCV, Spain Figure 1

Runs of homozygosity provide a genome landscape picture of inbreeding and genetic history of European autochthonous and commercial pig breeds

ROHs are long stretches of DNA homozygous at each polymorphic position. The proportion of genome covered by ROHs and their length are indicators of the level and origin of inbreeding. Frequent common ROHs within the same population define ROH islands and indicate hotspots of selection. In this work, we investigated ROHs in a total of 1131 pigs from 20 European local pig breeds and in three cosmopolitan breeds, genotyped with the GGP Porcine HD Genomic Profiler. plink software was used to identify ROHs. Size classes and genomic inbreeding parameters were evaluated. ROH islands were defined by evaluating different thresholds of homozygous SNP frequency. A functional overview of breed-specific ROH islands was obtained via over-representation analyses of GO biological processes. Mora Romagnola and Turopolje breeds had the largest proportions of genome covered with ROH (~1003 and ~955 Mb respectively), whereas Nero Siciliano and Sarda breeds had the lowest proportions (~207 and 247 Mb respectively). The highest proportion of long ROH (>16 Mb) was in Apulo-Calabrese, Mora Romagnola and Casertana. The largest number of ROH islands was identified in the Italian Landrace (n = 32), Cinta Senese (n = 26) and Lithuanian White Old Type (n = 22) breeds. Several ROH islands were in regions encompassing genes known to affect morphological traits. Comparative ROH structure analysis among breeds indicated the similar genetic structure of local breeds across Europe. This study contributed to understanding of the genetic history of the investigated pig breeds and provided information to manage these pig genetic resources.

Genome-wide detection of copy number variants in European autochthonous and commercial pig breeds by whole-genome sequencing of DNA pools identified breed-characterising copy number states

In this study, we identified copy number variants (CNVs) in 19 European autochthonous pig breeds and in two commercial breeds (Italian Large White and Italian Duroc) that represent important genetic resources for this species. The genome of 725 pigs was sequenced using a breed-specific DNA pooling approach (30-35 animals per pool) obtaining an average depth per pool of 42×. This approach maximised CNV discovery as well as the related copy number states characterising, on average, the analysed breeds. By mining more than 17.5 billion reads, we identified a total of 9592 CNVs (~683 CNVs per breed) and 3710 CNV regions (CNVRs; 1.15% of the reference pig genome), with an average of 77 CNVRs per breed that were considered as private. A few CNVRs were analysed in more detail, together with other information derived from sequencing data. For example, the CNVR encompassing the KIT gene was associated with coat colour phenotypes in the analysed breeds, confirming the role of the multiple copies in determining breed-specific coat colours. The CNVR covering the MSRB3 gene was associated with ear size in most breeds. The CNVRs affecting the ELOVL6 and ZNF622 genes were private features observed in the Lithuanian Indigenous Wattle and in the Turopolje pig breeds respectively. Overall, the genome variability unravelled here can explain part of the genetic diversity among breeds and might contribute to explain their origin, history and adaptation to a variety of production systems.

Abstract P3-07-09: ERRβ copy number and expression in triple negative breast cancer

Introduction: Triple negative breast cancer (TNBC) is a highly aggressive form of breast cancer prevalent in African-American (AA) women defined as estrogen receptor- (ER), progesterone receptor- (PR), and human epidermal growth factor receptor 2- (HER2) negative. Because ER- and HER2-targeted therapies are ineffective in TNBC, systemic chemotherapy is the standard of care and there is a tremendous need for new effective therapies with less toxicity. Steroid hormone receptors are highly druggable targets, and orphan nuclear receptors, members of the nuclear receptor superfamily, are emerging as targets for cancer therapy. In fact, we have previously shown that treatment of TNBC cells with a small molecule agonist ligand (DY131) for estrogen related receptor beta (ERRβ), has growth inhibitory and anti-mitotic activity. We have also shown that increased mRNA expression of ERRβ, correlates with better recurrence- and distant metastasis-free survival in TNBC/basal-like breast cancer. The goal of our current work is to comprehensively characterize ERRβ copy number and mRNA status in TNBC and determine its association with patients' prognosis.

Methods: ESRRB copy number was determined in 106 primary breast tumors (TNBC n=56, nonTNBC n=50) by array-CGH, using the Agilent SurePrint G3 Human CGH platform. ESRRB mRNA data and its association with overall survival was determined in systemically untreated patients from METABRIC using Illumina gene expression array data (probe ID ILMN_1707398).

Results: Copy number alterations (CNAs). Copy number losses at the ESRRB locus (14q24.3) were observed in 10/56 (17.8%) of TNBC vs. 10/50 (20%) of nonTNBC, while copy number gains were detected in 43/56 (76.8%) of TNBC vs. 29/50 (58%) of nonTNBC (c2 *p=0.036). Interestingly, in both TNBC and non-TNBC, ESRRB loss was seen with markedly higher frequency in AA patients when compared to Caucasian (CA) patients (c2 *p=0.012 for TNBC, p=0.052 for non-TNBC). mRNA expression. Among patients not treated with systemic chemotherapy in the METABRIC dataset, low ESRRB mRNA was significantly associated with shorter overall survival in TNBC, but not ER+ or HER2+ patients (TNBC hazard ratio 0.24, 95% confidence interval 0.07-0.85, *p=0.016). Low ESRRB also correlated with reduced overall survival in TP53 mutant (but not wild type) tumors (hazard ratio 0.28, 95% confidence interval 0.1-0.82, *p=0.013).

Conclusions: ESRRB presents significantly high levels of copy number losses in TNBC when compared to non-TNBC tumors. In breast tumors from AA women, both the TNBC and non-TNBC subtypes are significantly more likely to have reduced ESRRB copy number vs. CA women. Low ESRRB mRNA expression predicts for poor overall survival in TNBC and TP53 mutant tumors. These data advocate that ERRβ expression has prognostic value in breast cancer, particularly TNBC. Future goals include immunohistochemistry staining, and analysis, of a tissue microarray consisting of 150 primary breast tumors (50 TNBC, 50 ER+, 50 HER2+); as well as ERRβ overexpression and knock-down studies in TNBC cell lines to define the role it plays in TNBC.

Citation Format: Fernandez AI, Graham G, Győrffy B, Cavalli L, Mahajan A, Riggins RB. ERRβ copy number and expression in triple negative breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P3-07-09.

The mushroom body D1 dopamine receptor controls innate courtship drive

Mating is critical for species survival and is profoundly regulated by neuromodulators and neurohormones to accommodate internal states and external factors. To identify the underlying neuromodulatory mechanisms, we investigated the roles of dopamine receptors in various aspects of courtship behavior in Drosophila. Here, we report that the D1 dopamine receptor dDA1 regulates courtship drive in naïve males. The wild‐type naïve males actively courted females regardless their appearance or mating status. On the contrary, the dDA1 mutant (dumb) males exhibited substantially reduced courtship toward less appealing females including decapitated, leg‐less and mated females. The dumb male's reduced courtship activity was due to delay in courtship initiation and prolonged intervals between courtship bouts. The dampened courtship drive of dumb males was rescued by reinstated dDA1 expression in the mushroom body α/β and γ neurons but not α/β or γ neurons alone, which is distinct from the previously characterized dDA1 functions in experience‐dependent courtship or other learning and memory processes. We also found that the dopamine receptors dDA1, DAMB and dD2R are dispensable for associative memory formation and short‐term memory of conditioned courtship, thus courtship motivation and associative courtship learning and memory are regulated by distinct neuromodulatory mechanisms. Taken together, our study narrows the gap in the knowledge of the mechanism that dopamine regulates male courtship behavior.

A large-scale, rapid public health response to rabies in an organ recipient and the previously undiagnosed organ donor

This article describes and contrasts the public health response to two human rabies cases: one organ recipient diagnosed within days of symptom onset and the transplant donor who was diagnosed 18 months post-symptom onset. In response to an organ-transplant-related rabies case diagnosed in 2013, organ donor and recipient investigations were conducted by multiple public health agencies. Persons with potential exposure to infectious patient materials were assessed for rabies virus exposure. An exposure investigation was conducted to determine the source of the organ donor's infection. Over 100 persons from more than 20 agencies spent over 2700 h conducting contact investigations in healthcare, military and community settings. The 564 persons assessed include 417 healthcare workers [5.8% recommended for post-exposure prophylaxis (PEP)], 96 community contacts (15.6% recommended for PEP), 30 autopsy personnel (50% recommended for PEP), and 21 other persons (4.8% recommended for PEP). Donor contacts represented 188 assessed with 20.2% recommended for PEP, compared with 5.6% of 306 recipient contacts recommended for PEP. Human rabies cases result in substantial use of public health and medical resources, especially when diagnosis is delayed. Although rare, clinicians should consider rabies in cases of encephalitis of unexplained aetiology, particularly for cases that may result in organ donation.

Ion chemistry of NOO+

The kinetics for the reactions of NOO+ ions with neutral molecules having ionization potentials (IPs) from 9.27 to 15.58 eV was measured in a selected ion flow tube at 298 K. The NOO+ ions are produced from the reaction of N3+ + O2 and have been reacted with the following: NO, C6F6, CS2, CF3I, C3F6, OCS, C2H6, Xe, SO2, O3, N2O, CO2, Kr, CO, D2, and N2. Numerous types of reactions were observed with the various neutral reagents, including production of NO+ (which may involve loss of an O from the ion or addition of O to the neutral reactant, although the two channels could not be distinguished here), charge transfer, isomerization of NOO+ to ONO+, and hydride abstraction. High level theoretical calculations of the structures and energetics of the various isomers, electronic states, and transition states of NOO and NOO+ were performed to better understand the observed reactivity. All neutral species with an IP< or =11.18 eV were observed to react with NOO+ in part by charge transfer. Detailed calculations showed that the recommended adiabatic and vertical IPs of NOO are 10.4 and 11.7 eV, respectively, at the MRCISDQ/AVQZ level of theory. The observed experimental limit for charge transfer of 11.18 eV agreed well with the energetics of the final products obtained from theory if dissociation of the neutral metastable product occurred, i.e., the products were X+ +[O(3P) + NO(2Pi)], where [O(3P)+NO(2Pi)] formed via dissociation of metastable NOO. Charge exchange with neutral reagent X would, therefore, be exothermic if IP(X)<[IPad(NOO)-DeltaE(O+NO)-NOO]= approximately 11.1 eV, where IPad(NOO) is the adiabatic IP. The potential energy surface for the reaction of NOO+ with C2H6 was also calculated, indicating that two pathways for formation of HNO2 + C2H5 (+) exist.

Change of mechanical properties during short-term natural weathering of MSWI bottom ash

The present work describes the change of mechanical properties during the natural weathering of freshly quenched processed bottom ash. An unconfined uniaxial compression to failure test of the unbound material was used to determine compressive strength and modulus of elasticity. Three main stages of mechanical behavior were determined. In the first stage, during a period lower than 30 days, mechanical properties suddenly increase, with a compressive strength and elastic modulus 7 times greater than the initial parameters. During the second stage, compressive strength and modulus of elasticity lightly increase until approximately 90 days of curing time. Starting from this period both mechanical properties remain steady and independent of the curing time. The neoformed phases, the elevated water content, and the improvement of particle contact after compaction act as a binder layer among particles, increasing the mechanical parameters during the short-term natural weathering process. Because of this, the freshly compacted bottom ash progresses from behaving as an unbound material into a bound pavement material. These mechanical properties obtained from freshly quenched bottom ash are 6-7 times greater than those obtained from previously weathered bottom ash. The bottom ash expansion and leaching of metals were also evaluated.

Siderophore production by Aeromonas salmonicida subsp. salmonicida. Lack of strain specificity

Siderophore production, presence of iron-regulated outer membrane proteins and siderophore specificity was determined among 17 isolates of Aeromonas salmonicida subsp. salmonicida obtained from Spain and Scotland. All grew in the presence of ethylenediamine di(o-hydroxyphenylacetic acid) (EDDA) and siderophore production was detected using chrome azurol S (CAS) agar, confirming the presence of a high-affinity siderophore iron-uptake mechanism. The Arnow test confirmed that all isolates produced a catechol siderophore. Cross-feeding assays with indicator bacteria showed the absence of anguibactin, enterobactin, 2,3-dihydroxybenzoic acid (DHBA) and the hydroxamate siderophore, aerobactin, in the iron-restricted supernants of a representative isolate which cross fed 15/17 A. salmonicida isolates tested. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) showed the presence of the same 2 major iron-regulated outer membrane proteins (IROMPs) in all isolates when grown in iron-restricted conditions and siderophore strain specificity as assessed by cross-feeding experiments was not apparent. Thus, with respect to IROMP and siderophore production A. salmonicida appears to be a homogeneous species.

Effects of phorbol 12,13-dibutyrate and H-7 in extravascular smooth muscle contraction

The effect of the activator, phorbol 12,13-dibutyrate (PDB), and the inhibitor, H-7, of protein kinase C (PKC) has been assayed in rat uterus. PDB increases the amplitude of spontaneous contractions of rat uterus and this effect does not occur in the presence of H-7 or nifedipine. PDB did not modify the KCl-induced tonic contraction but H-7 relaxed it, in a concentration-dependent way. PDB inhibited the contraction induced by oxytocin in rat uterus incubated in Ca-free solution and relaxed the tonic contraction induced by oxytocin in this medium. The relaxing effect of PDB on oxytocin-induced contraction was not modified by H-7. Thus H-7 relaxed, in a concentration-dependent way, the tonic contractions induced by oxytocin and vanadate in the rat uterus incubated in Ca-free medium. Our results suggest a dual effect of PDB related to calcium, and a direct and PKC-independent inhibitory effect of H-7.

Differential effect of calcium and Bay K 8644 on the inhibitory action of estrogens in the rat uterus

1. The effects of the estrogens estradiol (E2, 10(-7) to 3 x 10(-5) M) and diethylstilbestrol (DES, 10(-7) to 3 x 10(-6) M) on tonic contractions of the rat uterus induced by KCl and CaCl2 have been studied. 2. E2 and DES relaxed, in a dose-dependent way, the tonic contraction induced by KCl (60 mM) (IC50: 5.16 +/- 1.49 x 10(-6) and 4.51 +/- 0.03 x 10(-7) M); the tonic contraction induced by CaCl2 (3 mM) in the rat uterus incubated in depolarizing Krebs (127 mM of K+) have also been relaxed (IC50: 8.6 +/- 0.03 x 10(-7) and 2.56 +/- 0.07 x 10 M) by both drugs. 3. The CaCl2 (0.1 to 10 mM) counteracted the relaxing effect of E2 and DES, respectively, up to 28.13 +/- 10.2% and 34.71 +/- 11.5%, on KCl-induced contractions, and up to 126.36 +/- 19.35% and 95.8 +/- 16.3% on CaCl2-induced contractions. 4. Bay K 8644 (10(-10) to 10(-6) M) reversed the relaxing effect of E2 and DES, respectively, up to 42.49 +/- 2.28% and 43.31 +/- 3.59% on KCl-induced contractions, and up to 21.73 +/- 4.16% and 75.97 +/- 9.63% on CaCl2-induced contractions. 5. Propranolol (10(-6) M) did not modify the relaxing effect of E2 or DES on CaCl2-induced contractions.

Mediators involved in the rat uterus contraction in calcium-free solution

1. The effect of (Na+ + K+)-ATPase inhibitor ouabain (10(-5)-3 x 10(-4) M), and the (Ca2+ + Mg2+)-ATPase inhibitors vanadate (6 x 10(-6)-6 x 10(-4) M), oxytocin (2 x 10(-9)-4 x 10(-8) M, and prostaglandin F2 alpha (PGF2 alpha, 10(-7)-6 x 10(-6) M) were assayed on rat uterus incubated in Ca-free medium. 2. Vanadate, oxytocin and PGF2 alpha, but not ouabain, induced contractions in a dose-dependent way (ED50: 7.5 +/- 0.03 x 10(-5) M; 6.5 +/- 0.064 x 10(-9) M and 3.8 +/- 0.085 x 10(-7) M). 3. Vanadate (3 x 10(-4) M) and oxytocin (OT, 10 mU/ml = 2 x 10(-8) M)-induced tonic contraction were not modified by nifedipine (10(-10)-10(-6) M), monensin (10(-5)-3 x 10(-4) M) or amiloride (10(-5)-10(-3) M). 4. The intracellular calcium release inhibitors TMB-8 (10(-6)-10(-4) M) and dantrolene (3 x 10(-6)-10(-4) M), and the prostaglandin release inhibitor indomethacin (3 x 10(-8)-6 x 10(-5) M) relaxed the vanadate and OT-induced tonic contractions. 5. The calmodulin inhibitors trifluoperazine (3 x 10(-5)-3 x 10(-4) M), bepridil (10(-8)-3 x 10(-4) M), calmidazolium (10(-7)-10(-4) M) and W-7 (10(-7)-10(-5) M) also relaxed the vanadate and OT-induced tonic contractions. 6. Our results suggest that oxytocin and vanadate-induced contractions on rat uterus in Ca-free medium could be produced by release of prostaglandins and intracellular calcium, and mediated by calmodulin.