T-type Ca2+ channel blockers prevent cardiac cell hypertrophy through an inhibition of calcineurin-NFAT3 activation as well as L-type Ca2+ channel blockers.

T-type Ca2+ channels (TCCs) are involved in cardiac cell growth and proliferation in cultured cardiomyocytes. Underlying molecular mechanisms are not well understood. In this study, we investigated the role of TCCs in signal transduction in cardiac hypertrophy compared with L-type Ca2+ channels (LCCs). Cardiomyocytes dissociated from neonatal mouse ventricles were cultured until stabilization. Cell hypertrophy was induced by reapplication of 1% fatal bovine serum (FBS) following a period (24 h) of FBS depletion. Cell surface area increased from 862+/-73 microm2 to 2153+/-131 microm2 by FBS stimulation in control (250+/-1.8%). T-type Ca2+ current (I(CaT)) was inhibited dose-dependently by kurtoxin (KT) and efonidipine (ED) with IC50 0.07 microM and 3.2 microM, respectively in whole-cell voltage clamp. On the other hand, 1 microM KT which inhibits I(CaT) over 90% did not effect on L-type Ca2+ current (I(CaL)). 10 microM ED had the ability of I(CaL) blockade as well as that of I(CaT) blockade. 3 microM nisoldipine (ND) suppressed I(CaL) by over 80%. The increase in cell surface area following reapplication of FBS as observed in control (250+/-1.8%) was significantly reduced in the presence of 1 microM KT (216+/-1.2%) and virtually abolished in the presence of 10 microM ED (97+/-0.8%) and 3 microM ND (80+/-1.1%). Hypertrophy was associated with an increase in BNP mRNA of 316+/-3.6% in control and this increase was reduced as well in the presence of 1 microM KT (254+/-1.8%) and almost abolished in the presence of 10 microM ED (116+/-1.1%) and 3 muM ND (93+/-0.8%). Immunolabeling showed that translocation of nuclear factor of activated T cells (NFAT3) into the nucleus in response to FBS stimulation was markedly inhibited by either KT or ED as well as ND. Calcineurin phosphatase activity was upregulated 2.2-fold by FBS, but KT, ED and ND decreased this upregulation (1.7-fold, 0.8-fold, and 0.7-fold with KT, ED and ND respectively). These results suggest that blockade of Ca2+ entry into cardiomyocytes via TCCs may block pathophysiological signaling pathways leading to hypertrophy as well as via LCCs. The mechanism may be the inhibition of calcineurin-mediated NFAT3 activation resulting in prevention of its translocation into the nucleus.

Efficacy of total intravenous anesthesia without intubation for laryngeal framework surgery.

CONCLUSION: Total intravenous anesthesia (TIVA) without intubation has the advantages of both conventional general anesthesia and local anesthesia. It is useful in laryngeal framework surgery because intraoperative voice monitoring while the patient remains awake is required. OBJECTIVE: In laryngeal framework surgery, it is desirable to monitor the voice during surgery. However, surgery is conducted under general anesthesia, although such a procedure renders the patient unable to phonate during surgery. We conducted TIVA without intubation, allowing patients to breathe spontaneously while undergoing operation, and succeeded in intraoperative voice monitoring with satisfactory postoperative voice production. SUBJECTS AND METHODS: The subjects were 21 patients who underwent surgery. For TIVA, propofol and pentazocine were used as a sedative and analgesic, respectively. A bispectral index (BIS) monitor was used to measure the depth of the anesthesia. Before the vocal folds were to be rotated, propofol administration was interrupted to arouse and instruct the patient to phonate. Guided by the phonation, the vocal folds were correctly positioned. Then propofol administration was resumed, and the wound was closed. RESULTS: The BIS value during continued administration of propofol was around 60, but exceeded 90 in all patients within 233.6 +/- 64.5 s after cessation. They clearly remembered the conversation they had with us during surgery.

[General anesthesia for thyroplasty employing voice test].

BACKGROUND: We reported an anesthetic technique for thyroplasty employing voice test. Thyroplasty is performed to improve voice quality in patients with unilateral vocal cord paralysis. Correct displacement of the vocal cord is assessed by asking the patient to phonate. At this point all patients should have recovered from general anesthesia and cooperate to phonation, facilitating correct displacement of the vocal cords. METHODS: Anesthesia was induced with i.v. pentazocine 15-30 mg and continuous propofol infusion 10 mg x kg(-1) x hr(-1). The patients received propofol infusion 4-6 mg x kg(-1) x hr(-1) with spontaneous ventilation. At the point of correct displacement of the vocal cords, we stopped propofol infusion and all the patients woke up immediately and cooperated. After determining the voice propofol was given at a rate of 4-6 mg x kg(-1) x hr(-1). RESULTS: The average times of surgery and anesthesia were 98 +/- 23 min and 139 +/- 22 min, respectively. At the point of correct displacement of the vocal cords, the average time from the end of propofol infusion until awakening with good quality of recovery was 313 +/- 93 sec. No patients complained of pain during or after CONCLUSIONS: This anesthetic technique provided both optimal operating conditions and patient comfort without serious complications.

Aldosterone modulates I(f) current through gene expression in cultured neonatal rat ventricular myocytes.

Mineralocorticoid receptor (MR) antagonists decrease the incidence of sudden cardiac death in patients with heart failure, as has been reported in two clinical trials (Randomized Aldactone Evaluation Study and Eplerenone Post-Acute Myocardial Infarction Heart Failure Efficacy and Survival Study). Aldosterone has been shown to increase the propensity to arrhythmias by changing the expression or function of various ion channels. In this study, we investigate the effect of aldosterone on the expression of hyperpolarization-activated current (I(f)) channels in cultured neonatal rat ventricular myocytes, using the whole cell patch-clamp technique, real-time PCR, and Western blotting. Incubation with 10 nM aldosterone for 17-24 h significantly accelerates the rate of spontaneous beating by increasing diastolic depolarization. I(f) current elicited by hyperpolarization from -50 to -130 mV significantly increases aldosterone by 10 nM (by 1.9-fold). Exposure to aldosterone for 1.5 h increases hyperpolarization-activated cyclic nucleotide-gated (HCN) 2 mRNA by 26.3% and HCN4 mRNA by 47.2%, whereas HCN1 mRNA expression remains unaffected. Aldosterone (24-h incubation) increases the expression of HCN2 protein (by 60.0%) and HCN4 protein (by 84.8%), but not HCN1 protein. MR antagonists (1 microM eplerenone or 0.1 microM spironolactone) abolish the increase of I(f) channel expression (currents, mRNA, and protein levels) by 10 nM aldosterone. In contrast, 1 microM aldosterone downregulated I(f) channel gene expression. Glucocorticoid receptor antagonist (100 nM RU-38486) did not affect the increase of I(f) current by 10 nM aldosterone. These findings suggest that aldosterone in physiological concentrations upregulates I(f) channel gene expression by MR activation in cardiac myocytes and may increase excitability, which may have a potential proarrhythmic bearing under pathophysiological conditions.

Pathophysiological significance of T-type Ca2+ channels: expression of T-type Ca2+ channels in fetal and diseased heart.

Re-expression of fetal genes has been considered to underlie ionic remodeling in diseased heart. T-type Ca(2+) channels have been reported to be functionally expressed in embryonic hearts. In this review, we summarize developmental changes of T-type Ca(2+) channels in mouse ventricles from 9.5 days postcoitum (dpc) to adulthood, using patch clamp and quantitative PCR. In addition, we introduced T-type Ca(2+) channel expression in hypertrophied ventricles caused by myocardial infarction (MI) and aortic banding (AOB). Substantial T-type Ca(2+) channel current was recorded at both 9.5 and 18 dpc. The currents were inhibited by Ni(2+) at low concentrations. The current was not detectable in the adult stage. Ca(v)3.2 (alpha(1H)) mRNA is expressed dominantly at both 9.5 and 18 dpc. Ca(v)3.1 (alpha(1G)) increases from 9.5 to 18 dpc, but remains at low level compared with Ca(v)3.2. In contrast, Ca(v)3.1 is greater than Ca(v)3.2 at the adult stage. In MI, Ca(v)3.1 mRNA correlates negatively with brain natriuretic peptide (BNP) mRNA, whereas Ca(v)3.2 mRNA correlates positively with BNP mRNA. In AOB, these correlations are weak. We also analyzed the neuron-restrictive silencer factor (NRSF) in these hearts because it is the suppressor of transcription of the fetal cardiac gene program. The negative correlation between NRSF and BNP was stronger in MI than in AOB. Our findings show that Ca(v)3.2 underlies the functional T-type Ca(2+) channel in embryonic heart and suggest that NRSF may regulate Ca(v)3.2 expression in diseased hearts.