Small-volume vitrification and rapid warming yield high survivals of one-cell rat embryos in cryotubes†.

To cryopreserve cells, it is essential to avoid intracellular ice formation during cooling and warming. One way to achieve this is to convert the water inside the cells into a non-crystalline glass. It is currently believed that to accomplish this vitrification, the cells must be suspended in a very high concentration (20-40%) of a glass-inducing solute, and subsequently cooled very rapidly. Herein, we report that this belief is erroneous with respect to the vitrification of one-cell rat embryos. In the present study, one-cell rat embryos were vitrified with 5 µL of EFS10 (a mixture of 10% ethylene glycol (EG), 27% Ficoll, and 0.45 M sucrose) in cryotubes at a moderate cooling rate, and warmed at various rates. Survival was assessed according to the ability of the cells to develop into blastocysts and to develop to term. When embryos were vitrified at a 2613 °C/min cooling rate and thawed by adding 1 mL of sucrose solution (0.3 M, 50 °C) at a warming rate of 18 467 °C/min, 58.1 ± 3.5% of the EFS10-vitrified embryos developed into blastocysts, and 50.0 ± 4.7% developed to term. These rates were similar to those of non-treated intact embryos. Using a conventional cryotube, we achieved developmental capabilities in one-cell rat embryos by rapid warming that were comparable to those of intact embryos, even using low concentrations (10%) of cell-permeating cryoprotectant and at low cooling rates.

Requirement of the Ca2+ channel ß2 subunit for sympathetic PKA phosphorylation.

Facilitation of cardiac function in response to signals from the sympathetic nervous system is initiated by the phosphorylation of L-type voltage-dependent Ca2+ channels (VDCCs) by protein kinase A (PKA), which in turn is activated by ß-adrenoceptors. Among the five subunits (α1, ß, α2/δ, and γ) of VDCCs, the α1 subunit and the family of ß subunits are substrates for PKA-catalyzed phosphorylation; however, the subunit responsible for ß-adrenergic augmentation of Ca2+ channel function has yet to be specifically identified. Here we show that the VDCC ß2 subunit is required for PKA phosphorylation upon sympathetic acceleration. In mice with ß2 subunit-null mutations, cardiac muscle contraction in response to isoproterenol was reduced and there was no significant increase in Ca2+ channel currents upon PKA-dependent phosphorylation. These findings indicate that within the sympathetic nervous system the ß2 subunit of VDCCs is required for physiological PKA-dependent channel phosphorylation.

Medaka as a model for ECG analysis and the effect of verapamil.

The heart of the medaka, a small fish native to East Asia, has electrophysiological aspects similar to mammalian hearts. We found that the heart rates of medaka were more similar to humans than mice or rats. Medaka exhibited similar electrocardiogram patterns to those of humans, suggesting a similarity in cardiac impulse formation and propagation. Their hearts also exhibited similar responsiveness to verapamil, a calcium channel antagonist; atropine, a parasympathetic nerve blocker; propranolol, a sympathetic ß-adrenergic blocker; and isoproterenol, a sympathetic ß-adrenergic agonist. We successfully analyzed action potentials and cardiac contractile forces in vivo. Verapamil affected action potential duration and reduced heart rate, suggesting the importance of voltage-dependent calcium channels in determining the heart rhythm of medaka. We also analyzed the expression of the voltage-dependent calcium channel ß2 subunit, which participates in channel formation in cardiac myocytes, and found that splice variant type-2 was the only major transcript in the heart. Our results indicate that medaka could be an appropriate animal model for studying cardiovascular pharmacology.

Modified sympathetic nerve regulation in AKAP5-null mice.

Genetic analyses have revealed an important association between A-kinase anchoring proteins (AKAPs) and the intracellular calcium modulating system. AKAP5, also known as AKAP79/150, is an anchoring protein between PKA and voltage-dependent calcium channels, ryanodine receptor-2, phospholamban and other molecules. The aim of the present study was to elucidate the physiological importance of AKAP5 in the creation of cardiac rhythm using AKAP5-null mice. ECG analysis showed a normal sinus rhythm and a decreased responsiveness to isoproterenol in AKAP5-null mice compared with wild-type mice. Analysis of heart rate variability revealed that the R-R interval was unstable in AKAP5-null mutants and that the low-frequency components had decreased, indicating that the tonus of the sympathetic nervous system was affected. Furthermore, the atrium of the AKAP5-null mice showed a decreased positive inotropic response to isoproterenol, indicating the involvement of AKAP5 in a PKA-dependent pathway. Thus, our present study revealed that AKAP5 plays a significant role in the regulation of sympathetic nerve activities.

In vitro effect of nicorandil on the carbachol-induced contraction of the lower esophageal sphincter of the rat.

The lower esophageal sphincter (LES) is a specialized region of the esophageal smooth muscle that allows the passage of a swallowed bolus into the stomach. Nitric oxide (NO) plays a major role in LES relaxation. Nicorandil possesses dual properties of a NO donor and an ATP-sensitive potassium channel (KATP channel) agonist, and is expected to reduce LES tone. This study investigated the mechanisms underlying the effects of nicorandil on the LES. Rat LES tissues were placed in an organ bath, and activities were recorded using an isometric force transducer. Carbachol-induced LES contraction was significantly inhibited by KATP channel agonists in a concentration-dependent manner; pinacidil >> nicorandil ≈ diazoxide. Nicorandil-induced relaxation of the LES was prevented by pretreatment with glibenclamide, whereas N(G)-nitro-l-arginine methyl ester (l-NAME), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) and iberiotoxin were ineffective at preventing nicorandil-induced LES relaxation. Furthermore, nicorandil did not affect high K(+)-induced LES contraction. Reverse-transcription polymerase chain reaction analysis and immunohistochemistry revealed expression of KCNJ8 (Kir6.1), KCNJ11 (Kir6.2), ABCC8 (SUR1) and ABCC9 (SUR2) subunits of the KATP channel in the rat lower esophagus. These findings indicate that nicorandil causes LES relaxation chiefly by activating the KATP channel, and that it may provide an additional pharmacological tool for the treatment of spastic esophageal motility disorders.

Age-related effects of dexmedetomidine on myocardial contraction and coronary circulation in isolated guinea pig hearts.

Dexmedetomidine is a selective α2 adrenergic agonist. Although dexmedetomidine is widely used for sedation and analgesia, it frequently produces hypotension and bradycardia. The present study aimed to evaluate the effects of dexmedetomidine on cardiac function and coronary circulation using Langendorff-perfused guinea pig hearts. Coronary perfusion pressure (CPP) and left ventricular pressure (LVP) were continuously monitored, and electric field stimulation (EFS) was applied to stimulate sympathetic nerve terminals. Dexmedetomidine almost completely inhibited the EFS-induced increase in LVP at all ages. The effect of dexmedetomidine on coronary artery resistance varied according to postnatal age, i.e., dexmedetomidine had little effect on CPP in young hearts (<4 weeks) but increased CPP by 10 mmHg at 4-8 weeks and by 15 mmHg at >8 weeks. The increase in CPP in adult hearts was inhibited by imiloxan, an α2B antagonist, and prazosin, an α1 antagonist. The results suggest that dexmedetomidine acts on α2 adrenergic receptors at sympathetic nerve terminals to suppress the release of norepinephrine. In addition, the findings suggest that dexmedetomidine directly affects α1 adrenoceptors and/or α2B adrenoceptors on coronary smooth muscles to increase CPP. The age-related changes in α adrenoceptor subtypes may be linked to the cardiodepressant effects of dexmedetomidine.

Linkage of sleep-disordered breathing and acute aortic dissection with patent false lumen.

Sleep-disordered breathing (SDB) is known as a cardiovascular risk factor and has high prevalence in hypertension, which is a major risk factor of aortic dissection (AD). However, the impact of SDB on AD has not been fully clarified. The aim of this study is to elucidate the impact of SDB on AD, especially on the type of false lumen in AD. We enrolled twenty-three consecutive patients with acute AD (mean age: 66 ± 13 years). All subjects were evaluated by an ambulatory polygraphic sleep monitoring within 1 month from the onset. AD was evaluated by axial images of computed tomography. We comparatively analyzed SDB and AD. 35 % of the subjects presented severe OSA (apnea-hypopnea index: AHI ≥30). The patent false lumen group showed significantly higher systolic and diastolic blood pressure (BP) on arrival and AHI, and lower percutaneous oxygen saturation (SaO2) compared with those in the thrombosed false lumen group. The prevalence of severe SDB was higher in the patent false lumen group (60 vs 15 %, p = 0.039). Systolic BP on arrival was significantly correlated with AHI (r = 0.457, p = 0.033) and the minimum SaO2 (r = -0.537, p = 0.010). The present study revealed close linkage between SDB and AD, and a high prevalence of SDB among AD patients. Severe SDB was related to the development of AD, especially for the patent false lumen type through highly elevated BP which might be easily evoked in the presence of severe SDB. Repetitive occurrence of intrathoracic negative pressure also might influence the repair or closure of false lumen of AD, although the present analysis did not reach statistical significance.

Volume elastic modulus of the brachial artery and coronary artery stenosis in patients with suspected stable coronary artery disease.

This study aimed to examine the association between the non-invasive measurement of the brachial artery volume elastic modulus (V E), an index of arterial stiffness, and the presence of coronary artery stenosis in patients with suspected stable coronary artery disease (CAD). A total of 135 patients with suspected stable CAD (87 men, mean age, 64 ± 12 years) underwent oscillometric measurement of the brachial artery to obtain V E. Coronary angiography was thereafter carried out to diagnose CAD, defined as having ≥75 % stenosis in the epicardial coronary arteries. V E was significantly higher in patients with CAD (1.94 ± 0.34 mmHg/%) than in those without CAD (1.71 ± 0.35 mmHg/%, P < 0.001). In multiple logistic regression analysis, V E was an independent predictor for the presence of CAD (odds ratio 1.19 per 0.1 mmHg/% increase, 95 % CI 1.04-1.51) even after adjusting for multiple potential confounders including the Framingham risk score (FRS). The area under the curve of the receiver operating characteristic curve analysis for discriminating CAD increased significantly after the addition of V E to the FRS (from 0.75 to 0.81, P = 0.034). The category-free net reclassification improvement and the integrated discrimination improvement by adding V E to the FRS were 0.476 (95 % CI 0.146-0.806) and 0.086 (95 % CI 0.041-0.132), respectively. In conclusion, the brachial V E was significantly associated with the presence of coronary artery stenosis. The additional measurement of V E to the FRS improved the ability to identify patients with coronary artery stenosis among those with suspected stable CAD.

Modified autonomic regulation in mice mutated in the ß4 subunit of the lh/lh calcium channel.

Genetic analyses have revealed an important association between P/Q-type calcium channel activities and hereditary neurological disorders. The P/Q-type channels are composed principally of heterologous multimeric subunits including CaV2.1 and CaVß4. Of these, the ß4 subunit is thought to play a significant role in channel physiology, because a mouse line mutant in that subunit (the lethargic mouse: lh) exhibits a severe ataxic phenotype. The aim of the present study was to elucidate the physiological importance of the ß4 subunit. ECG analysis showed that the T wave was high in 8-week-old lh mutants; this may be associated with hyperkalemia. Upon pharmacological ECG analysis, 2-3-week-old lh mutants exhibited reduced responses to a ß-blocker and a muscarinic receptor antagonist. Analysis of heart rate variability revealed that the R-R interval was unstable in lh mutants and that both the low- and high-frequency components had increased in extent, indicating that the tonus of both the sympathetic and parasympathetic nervous systems was modified. Thus, our present study revealed that the ß4 subunit played a significant role in regulation of sympathetic and parasympathetic nerve activities.

Involvement of the histamine H1 receptor in the regulation of sympathetic nerve activity.

The histamine system is involved in the regulation of the autonomic nervous system. We used gene-targeted mice to investigate the role of histamine receptors in the regulation of the sympathetic nervous system. Reverse transcription-polymerase chain reaction (RT-PCR) analysis revealed histamine H1, H2, and H3 receptor expression in the superior cervical ganglion, which contains sympathetic nerve cell bodies. We measured the heart rate variability (HRV), the changes in the beat-to-beat heart rate, which is widely used to assess autonomic activity in the heart. H1 blockade attenuated the baroreflex-mediated changes in heart rate in wild-type (WT) mice, whereas the heart rate response to H2- and H3-specific blockers was unaffected. l-Histidine decarboxylase (HDC) expression in the superior cervical ganglion of H1R-null mice was higher than that in WT controls, whereas the enzyme levels in H2R- and H3R-null mice were not significantly different from those in the WT. All mutant mice (H1R-, H2R-, and H3R-null mice) showed normal electrocardiogram (ECG) patterns with little modification in ECG parameters and the expected response to the ß-adrenergic blocker propranolol. Similar to our findings in WT mice, H1 blockade attenuated the baroreflex-mediated heart rate change in H1R-null mice, whereas the heart rate response was unaffected in H2R- and H3R-null mice. The HRV analysis revealed relatively unstable RR intervals, an increased standard deviation of the interbeat interval (SDNN), and low-frequency (LF) component in H1R-null mice compared with the other groups, suggesting that sympathetic nerve activity was altered in H1R-null mice. Taken together, our findings indicate that H1 receptors play a major role in the regulation of sympathetic nerve activity.

Involvement of the orexin system in sympathetic nerve regulation.

Orexin, also known as hypocretin, is a secreted neuropeptide implicated in the regulation of sleep and food intake. In the present study, we examined the importance of orexin in regulation of the sympathetic nervous system using an orexin/ataxin-3 transgenic (OXTg) rat, which has a minimal number of orexin neurons. RT-PCR analysis identified expression of prepro-orexin and orexin receptor-1 (OX1R) in the superior cervical ganglion (SCG), and expression of another receptor (OX2R) was marginal in the wild-type rat. The orexin/ataxin-3 transgenic rat showed increased expression of OX1R and OX2R, whereas expression of prepro-orexin was undetectable, suggesting a compensatory increase in both receptors. In the ECG recording (R-R interval), orexin/ataxin-3 transgenic rats showed decreased responsiveness to the ß-adrenergic blocker propranolol. Furthermore, OXTg rats had deteriorated R-R interval regulation, indicating involvement of the orexin system in sympathetic nerve regulation. This was accompanied by decreased baroreflex and responsiveness to ß-adrenergic blocker in blood pressure recording, also suggesting involvement of the orexin system in sympathetic nerve regulation. Histological examination revealed hypotrophic changes in the transgenic heart, suggesting involvement of the orexin system in cardiac development. Taken together, our present results indicate involvement of the orexin system in sympathetic nerve control.

Microvascular resistance in response to iodinated contrast media in normal and functionally impaired kidneys.

Contrast-induced nephropathy (CIN) is considered to result from intrarenal vasoconstriction, and occurs more frequently in impaired than in normal kidneys. It was hypothesized that iodinated contrast media would markedly change renal blood flow and vascular resistance in functionally impaired kidneys. Thirty-six patients were enrolled (32 men; mean age, 75.3 ± 7.6 years) undergoing diagnostic coronary angiography and were divided into two groups based on the presence of chronic kidney disease (CKD), defined as an estimated glomerular filtration rate (eGFR) of < 60 mL/min per 1.73 m(2) (CKD and non-CKD groups, n = 18 in both). Average peak velocity (APV) and renal artery resistance index (RI) were measured by Doppler flow wire before and after administration of the iodinated contrast media. The APV and the RI were positively and inversely correlated with the eGFR at baseline, respectively (APV, R = 0.545, P = 0.001; RI, R = -0.627, P < 0.001). Mean RI was significantly higher (P = 0.015) and APV was significantly lower (P = 0.026) in the CKD than in the non-CKD group. Both APV (P < 0.001) and RI (P = 0.002) were significantly changed following contrast media administration in the non-CKD group, but not in the CKD group (APV, P = 0.258; RI, P = 0.707). Although renal arterial resistance was higher in patients with CKD, it was not affected by contrast media administration, suggesting that patients with CKD could have an attenuated response to contrast media.

Effects of propofol on electrocardiogram measures in mice.

We investigated the anesthetic effects of propofol on the electrocardiogram (ECG) in mice. We also compared the effects of isoflurane (2%) inhalation anesthesia, intraperitoneal propofol (50 or 100 mg/kg), and pentobarbital (50 mg/kg) on ECG in mice. Isoflurane inhalation and pentobarbital anesthesia were both associated with an acceptable heart rate (HR) range (ca. 450 - 500 bpm). In contrast, high-dose propofol anesthesia significantly decreased the HR. Importantly, propofol anesthesia led to significantly reduced responses to propranolol, a ß-blocker, suggesting that it affects sympathetic tonus and is not suitable for the evaluation of cardiovascular or sympathetic function. Propofol also reduced the response to atropine, indicative of suppression of mouse parasympathetic nerve activity. Our data suggest that propofol anesthesia should not be the first choice for cardiovascular analysis in mice.

Inhalation anesthesia is preferable for recording rat cardiac function using an electrocardiogram.

The effects of inhalation anesthesia (2% isoflurane, sevoflurane, or enflurane) and intraperitoneal anesthesia with pentobarbital (65 mg/kg) were compared in rats using an electrocardiogram (ECG) and determination of blood oxygen saturation (SPO2) levels. Following inhalation anesthesia, heart rate (HR) and SPO2 were acceptable while pentobarbital anesthesia decreased HR and SPO2 significantly. This indicates that inhalation anesthesia is more preferable than pentobarbital anesthesia when evaluating cardiovascular factors. Additionally, pentobarbital significantly increased HR variability (HRV), suggesting a regulatory effect of pentobarbital on the autonomic nervous system, and resulted in a decreased response of the baro-reflex system. Propranolol or atropine had limited effects on ECG recording following pentobarbital anesthesia. Taken together, these data suggest that inhalation anesthesia is suitable for conducting hemodynamic analyses in the rat.

Sildenafil prevents the up-regulation of transient receptor potential canonical channels in the development of cardiomyocyte hypertrophy.

BACKGROUND: Transient receptor potential canonical (TRPCs) channels are up-regulated in the development of cardiac hypertrophy. Sildenafil inhibits TRPC6 activation and expression, leading to the prevention of cardiac hypertrophy. However, the effects of sildenafil on the expression of other TRPCs remain unknown. We hypothesized that in addition to its effects of TRPC6, sildenafil blocks the up-regulation of other TRPC channels to suppress cardiomyocyte hypertrophy. METHODS AND RESULTS: In cultured neonatal rat cardiomyocytes, a 48 h treatment with 10nM endothelin (ET)-1 induced hypertrophic responses characterized by nuclear factor of activated T cells activation and enhancement of brain natriuretic peptide expression and cell surface area. Co-treatment with sildenafil (1 µM, 48 h) inhibited these ET-1-induced hypertrophic responses. Although ET-1 enhanced the gene expression of TRPCs, sildenafil inhibited the enhanced gene expression of TRPC1, C3 and C6. Moreover, co-treatment with sildenafil abolished the augmentation of SOCE in the hypertrophied cardiomyocytes. CONCLUSIONS: These results suggest that sildenafil inhibits cardiomyocyte hypertrophy by suppressing the up-regulation of TRPC expression.

Involvement of the orexin system in adrenal sympathetic regulation.

Orexin (hypocretin) is a neuropeptide secreted from hypothalamic neurons that is known to be activated during motivated behaviors and active waking. Presently, our knowledge of orexin is mainly limited to the central nervous system, and the involvement of the orexin system in peripheral tissues has received little attention. In the present study, we analyzed the existence of the orexin system in the adrenal medulla, which is part of the sympathetic nervous system. Orexin and its receptors are expressed in the bovine adrenal medulla. Orexins stimulated intracellular calcium changes and epinephrine release from cultured bovine adrenal medullary cells. Applied orexin decreased expression of prepro-orexin, orexin receptor-1 and orexin receptor-2, suggesting negative feedback regulation in the adrenal gland. Our results indicate involvement of the orexin system in the sympathetic regulation of the adrenal medulla.

Efficacy and limitations of oral inotropic agents for the treatment of chronic heart failure.

The heart failure guideline in Japan has stated the necessity of investigating the role of oral inotropic agents in patients with chronic heart failure (CHF), which are clinically available only in Japan. A total of 1,846 consecutive patients with heart failure (mean: 69.5 years old, 1,279 males) treated at our institute from November 2009 to August 2010 were investigated retrospectively. Thirty-one patients (1.84%) who had taken oral inotropic agents (pimobendan 27, docarpamine 6, and denopamine 4) were extracted for this study, and the efficacy and limitations of the treatments were analyzed. Following the oral inotropic treatment, the NYHA functional class (P = 0.017), cardiothoracic ratio (P = 0.002) and B-type natriuretic peptide levels (P = 0.011) were significantly improved, and the number of emergency room (ER) visits (P < 0.001) and hospitalizations (P < 0.001) were significantly reduced. The nonsurviving patients (n = 7/31, 22.6%) were significantly older (P = 0.02) and tended to have a larger cardiothoracic ratio (P = 0.084) compared with the survivors. An absence of concomitant beta-blocker therapy was significantly associated with a worse prognosis (oneyear mortality 2/21 versus 5/10, log rank, P = 0.011). Oral inotropic agents brought about improvements in the clinical parameters of CHF and a reduction in ER visits and hospitalizations. However, concomitant beta-blocker therapy should be considered for patients receiving oral inotropic treatment.

Arrhythmogenic coupling between the Na+ -Ca2+ exchanger and inositol 1,4,5-triphosphate receptor in rat pulmonary vein cardiomyocytes.

Atrial fibrillation, the most common sustained arrhythmia, is believed to be triggered by ectopic electrical activity originating in the myocardial sleeves surrounding the pulmonary veins (PVs). It has been reported that myocardial sleeves have the potential to generate automaticity in response to norepinephrine. This study investigated the cellular mechanisms underlying norepinephrine-induced automaticity in PV cardiomyocytes isolated from rats. Application of 10 µM norepinephrine to PV cardiomyocytes induced repetitive and transient increases in intracellular Ca(2+) concentrations. The Ca(2+) transient was accompanied by depolarization, and induced automatic rhythmic action potentials at approximately 4Hz in perforated patch clamp preparations in 27% of myocytes were observed. When the recording mode was switched from current-clamp to voltage-clamp mode during the continuous presence of automaticity, an oscillatory current was observed. The oscillatory current was always inward, irrespective of the membrane potential, indicating that the current was derived mainly from the Na(+)-Ca(2+) exchanger (NCX). The norepinephrine-induced automaticity was suppressed by blocking either the ß(1)- or α(1)-adrenoceptor. Additionally, this automaticity was blocked by inhibitors of phospholipase C and the inositol 1,4,5-triphosphate receptor (IP(3)R) but not by a protein kinase C inhibitor. We observed that the transverse-tubule system was enriched in cardiomyocytes in the PV, in contrast to those of the atrium, and that the NCX and IP(3)R were co-localized along transverse tubules. These findings suggest that a functional coupling between the NCX and IP(3)R causes arrhythmic excitability of the PV during the presence of combined ß(1)- and α(1)-adrenoceptor stimulation.

Malondialdehyde-modified low-density lipoprotein is a useful marker to identify patients with vulnerable plaque.

BACKGROUND: The association between elevated malondialdehyde-modified low-density lipoprotein (MDA-LDL) and plaque instability in patients with coronary artery disease (CAD) is suspected but not established. The aim of the present study was therefore to investigate the association between serum MDA-LDL and plaque characteristics on angioscopy. METHODS AND RESULTS: A total of 37 consecutive patients with CAD and single-vessel disease who underwent pre-interventional angioscopy, were studied. Using angioscopy at the target lesions, the presence of yellow plaque and complex plaque was examined. Moreover, we evaluated the yellow intensity, which has been shown to have an inverse correlation with the fibrous-cap thickness of the plaques, with quantitative colorimetry to identify a thin-cap atheroma. Serum MDA-LDL in patients with thin-cap atheroma diagnosed on quantitative colorimetry was significantly higher than in patients without thin-cap atheroma (P<0.0009). Univariate logistic regression indicated that serum MDA-LDL was a predictor for thin-cap atheroma (odds ratio [OR], 1.48; 95% confidence interval [CI]: 1.10-1.97; P=0.003) and for complex plaque (OR, 1.22; 95% CI: 1.00-1.48; P=0.046). On multivariate logistic regression serum MDA-LDL was the only independent predictor for thin-cap atheroma (OR, 1.48; 95% CI: 1.10-1.97; P=0.011). CONCLUSIONS: Using angioscopy and quantitative colorimetry, elevated MDA-LDL was confirmed to be associated with thin-cap atheroma in CAD patients.

Enhanced ß-adrenergic response in mice with dominant-negative expression of the PKD2L1 channel.

Polycystic kidney disease (PKD) is the most common genetic cause of kidney failure in humans. Among the various PKD-related molecules, PKD2L1 forms cation channels, but its physiological importance is obscure. In the present study, we established a transgenic mouse line by overexpressing the dominant-negative form of the mouse PKD2L1 gene (i.e., lacking the pore-forming domain). The resulting PKD2L1del-Tg mice exhibited supraventricular premature contraction, as well as enhanced sensitivity to ß-adrenergic stimulation and unstable R-R intervals in electrocardiography. During spontaneous atrial contraction, PKD2L1del-Tg atria showed enhanced sensitivity to isoproterenol, norepinephrine, and epinephrine. Action potential recording revealed a shortened action potential duration in PKD2L1del-Tg atria in response to isoproterenol. These findings indicated increased adrenergic sensitivity in PKD2L1del-Tg mice, suggesting that PKD2L1 is involved in sympathetic regulation.