AKAPs as antiarrhythmic targets?

Phosphorylation of ion channels plays a critical role in the modulation and amplification of biophysical signals. Kinases and phosphatases have broad substrate recognition sequences. Therefore, the targeting of kinases and phosphatases to specific sites enhances the regulation of diverse signaling events. Ion channel macromolecular complexes can be formed by the association of A-kinase anchoring proteins (AKAPs) or other adaptor proteins directly with the channel. The discovery that leucine/isoleucine zippers play an important role in the recruitment of phosphorylation-modulatory proteins to certain ion channels has permitted the elucidation of specific ion channel macromolecular complexes. Disruption of signaling complexes by genetic defects can lead to abnormal physiological function. This chapter will focus on evidence supporting the concept that ion channel macromolecular complex formation plays an important role in regulating channel function in normal and diseased states. Moreover, we demonstrate that abnormal complex formation may directly lead to abnormal channel regulation by cellular signaling pathways, potentially leading to arrhythmogenesis and cardiac dysfunction.

Association of habitual long-distance running with the thickness of skeletal muscles and subcutaneous fat in the body extremities and trunk in middle-aged men.

AIM: We investigated the association of habitual long-distance running with the thickness of skeletal muscles and subcutaneous fat in the body extremities and trunk in middle-aged men using ultrasonography. METHODS: Three groups of healthy middle-aged men [mean (SD), 62.1 (2.8) years] took part in this investigation: a high-level group of 11 master runners who had competed in a 42.195 km race and run 51.6 (21.7) km every week, an intermediary-level group of 10 master runners who had competed in a 5-20 km race and run 9.3 (4.9) km every week, and a low-level group of 7 untrained men who continued to do no systematic training. The muscle thickness at 8 sites and the subcutaneous fat thickness at 10 sites were measured by B-mode ultrasonography, and were compared among the 3 groups. RESULTS: The high-level group had 10.0(-1)5.2% higher values for muscle thickness at the erector spinae, hamstrings, tibialis anterior, and triceps surae, compared with the intermediary-level and the low-level groups (p<0.05-0.001). The thickness of the subcutaneous fat about the rectus abdominis and external oblique was lower in the high-level group than in the intermediary-level and the low-level groups (p<0.05). CONCLUSIONS: Middle-aged male master athletes who habitually run at a high level have more muscle thickness in the lower extremities and trunk, and less subcutaneous fat thickness in the central regions of the body than do middle-aged men who habitually run at an intermediary level or do not run at all.

Stimulation of protein kinase C inhibits bursting in disease-linked mutant human cardiac sodium channels.

BACKGROUND: Mutations in SCN5A, the gene coding for the human cardiac Na+ channel alpha-subunit, are associated with variant 3 of the long-QT syndrome (LQT-3). Several LQT-3 mutations promote a mode of Na+ channel gating in which a fraction of channels fail to inactivate, contributing sustained Na+ channel current (Isus), which can delay repolarization and prolong the QT interval. Here, we investigate the possibility that stimulation of protein kinase C (PKC) may modulate Isus, which is prominent in disease-related Na+ channel mutations. METHODS AND RESULTS: We measured the effects of PKC stimulation on Na+ currents in human embryonic kidney (HEK 293) cells expressing 3 previously reported disease-associated Na+ channel mutations (Y1795C, Y1795H, and DeltaKPQ). We find that the PKC activator 1-oleoyl-2-acetyl-sn-glycerol (OAG) significantly reduced Isus in the mutant but not wild-type channels. The effect of OAG on Isus was reduced by the PKC inhibitor staurosporine (2.5 micromol/L), ablated by the mutation S1503A, and mimicked by the mutation S1503D. Isus recorded in myocytes isolated from mice expressing DeltaKPQ channels was similarly inhibited by OAG exposure or stimulation of alpha1-adrenergic receptors by phenylephrine. The actions of phenylephrine on Isus were blocked by the PKC inhibitor chelerythrine. CONCLUSIONS: We conclude that stimulation of PKC inhibits channel bursting in disease-linked mutations via phosphorylation-induced alteration of the charge at residue 1503 of the Na+ channel alpha-subunit. Sympathetic nerve activity may contribute directly to suppression of mutant channel bursting via alpha-adrenergic receptor-mediated stimulation of PKC.

Leucine/isoleucine zipper coordination of ion channel macromolecular signaling complexes in the heart. Roles in inherited arrhythmias.

The sympathetic nervous system controls the force and rate of contraction of the heart. The rapid response to stress and exercise mediated by increased sympathetic nervous system (SNS) activity requires the coordinated regulation of several ion channels in response to activation of beta-adrenergic receptors. The microenvironment of target channels is mediated by the assembly of macromolecular signaling complexes in which targeting proteins recruit phosphatases and kinases and in turn bind directly to the channel protein via highly conserved leucine/isoleucine zippers (LIZs). Disruption of local signaling by disease-associated LIZ mutations unbalances the physiologic response to SNS stimulation and increases the risk of arrhythmia in mutation carriers.

Clostridium thermocellum cellulase CelT, a family 9 endoglucanase without an Ig-like domain or family 3c carbohydrate-binding module.

The celT gene of Clostridium thermocellum strain F1 was found downstream of the mannanase gene man26B [Kurokawa J et al. (2001) Biosci Biotechnol Biochem 65:548-554] in pKS305. The open reading frame of celT consists of 1,833 nucleotides encoding a protein of 611 amino acids with a predicted molecular weight of 68,510. The mature form of CelT consists of a family 9 cellulase domain and a dockerin domain responsible for cellulosome assembly, but lacks a family 3c carbohydrate-binding module (CBM) and an immunoglobulin (Ig)-like domain, which are often found with family 9 catalytic domains. CelT devoid of the dockerin domain (CelTDeltadoc) was constructed and purified from a recombinant Escherichia coli, and its enzyme properties were examined. CelTDeltadoc showed strong activity toward carboxymethylcellulose (CMC) and barley beta-glucan, and low activity toward xylan. The V(max) and K(m) values were 137 micro mol min(-1) mg(-1) and 16.7 mg/ml, respectively, for CMC. Immunological analysis indicated that CelT is a catalytic component of the C. thermocellum F1 cellulosome. This is the first report describing the characterization of a family 9 cellulase without an Ig-like domain or family 3c CBM.

Usefulness of flow-mediated dilation of the brachial artery and/or the intima-media thickness of the carotid artery in predicting coronary narrowing in patients suspected of having coronary artery disease.

It has been reported that flow-mediated dilation (FMD) of the brachial artery and the carotid intima-media thickness (IMT), markers of atherosclerosis, are altered in patients with coronary artery disease (CAD), but it is still not known if the presence of CAD can be detected using these markers. We examined whether the presence of CAD can be detected by FMD of the brachial artery and/or IMT. Eighty-one patients who underwent coronary angiography for the first time were enrolled. In each patient, brachial artery diameter responses to FMD and the administration of nitroglycerin spray, and carotid IMT were measured using high-resolution ultrasound (10 MHz) before coronary angiography. CAD was defined as >50% stenosis of a major coronary artery. Fifty-six patients had CAD. FMD was lower and IMT was greater in patients with CAD (FMD, 2.9 +/- 0.2% vs 9.4 +/- 0.5%; IMT, 1.09 +/- 0.05 vs 0.79 +/- 0.04 mm, both p <0.0001). Nitroglycerin-induced dilation did not differ in the 2 groups. Multivariate analysis showed that FMD was the only predictor of the presence of CAD (p = 0.0026). Receiver-operating characteristic analysis demonstrated that a cutoff value for FMD for detecting the presence of CAD was 6%, with a sensitivity of 0.93 (52 of 56) and a specificity of 0.88 (22 of 25). These findings suggest that FMD but not IMT may be used to detect the presence of CAD in patients with suspected CAD.

Endothelial dysfunction is an independent factor responsible for vasospastic angina.

In order to evaluate peripheral endothelial function in patients with vasospastic angina (VSA), we measured flow-mediated dilation (FMD) of the brachial artery in patients with VSA and compared it with FMD in patients without VSA. Endothelial dysfunction is considered one of the mechanisms underlying VSA. However, its exact role remains to be clarified. The study included 30 patients with positive spasm-provocational test results without evidence of significant coronary stenosis (VSA group) and 30 patients with negative spasm-provocational test results without evidence of significant coronary stenosis (control group). In each patient, brachial artery diameter responses to hyperemic flow and glyceryl trinitrate spray were measured using high-resolution ultrasound. The carotid intima-media thickness was also measured as a marker of systemic atherosclerosis. FMD was lower in the VSA group (4.8+/-0.5%) compared with the control group (9.4+/-0.7%, P<0.0001). In the VSA group, FMD was not affected by coronary risk factors or the presence of atherosclerotic changes on coronary angiography. Glyceryl trinitrate-induced dilation did not differ between the two groups. The intima-media thickness was comparable between the VSA (0.85+/-0.04 mm) and control groups (0.81+/-0.05 mm). These findings indicated that peripheral endothelial function is impaired only in the VSA group, whereas the atherosclerotic changes were similar in the two groups. We conclude that endothelial dysfunction may be an independent factor responsible for the development of VSA.

Molecular basis of the delayed rectifier current I(ks)in heart.

J. Kurokawa, H. Abriel and R. S. Kass. Molecular Basis of the Delayed Rectifier Current I(Ks)in Heart. Journal of Molecular and Cellular Cardiology (2001) 33, 873-882. Electrical activity underlies the control of the frequency, strength, and duration of contraction of the heart. During the cardiac cycle, a regular rhythmic pattern must be established in time-dependent changes in ionic conductances in order to ensure events that underlie normal cardiac function. This pattern must be tightly regulated by sympathetic nervous activity to ensure a physiologically relevant relationship between diastolic filling and ejection times with variable heart rate. The duration of the ventricular action potential is controlled in part by a slowly activated potassium channel current, I(Ks). The molecular identity of the subunits that comprise the channels conducting this current is important, not only for understanding the fundamental mechanisms that control electrical activity in healthy individuals, but also for understanding the molecular basis of at least one inherited human disease, LQTS-1. This brief review summarizes key points of information regarding the molecular determinants of the activity of these channels, their relationship to human disease, and what is known, and yet to be discovered, about the molecular determinants of the regulation of this channel by sympathetic nervous activity.

Sequence of the Clostridium thermocellum mannanase gene man26B and characterization of the translated product.

The man26B gene of Clostridium thermocellum strain F1 was found in pKS305, which had been selected as a recombinant plasmid conferring endoglucanase activity on Escherichia coli. The open reading frame of man26B consists of 1,773 nucleotides encoding a protein of 591 amino acids with a predicted molecular weight of 67,047. Man26B is a modular enzyme composed of an N-terminal signal peptide and three domains in the following order: a mannan-binding domain, a family 26 mannanase domain, and a dockerin domain responsible for cellulosome assembly. We found that this gene was a homologue of the man26A gene of C. thermocellum strain YS but that there were insertion or deletion mutations that caused a frame-shift mutation affecting a stretch of 26 amino acids in the catalytic domain. Man26B devoid of the dockerin domain was constructed and purified from a recombinant E. coli, and its enzyme properties were examined. Immunological analysis indicated that Man26B was a catalytic component of the C. thermocellum F1 cellulosome.

TEA(+)-sensitive KCNQ1 constructs reveal pore-independent access to KCNE1 in assembled I(Ks) channels.

I(Ks), a slowly activating delayed rectifier K(+) current through channels formed by the assembly of two subunits KCNQ1 (KvLQT1) and KCNE1 (minK), contributes to the control of the cardiac action potential duration. Coassembly of the two subunits is essential in producing the characteristic and physiologically critical kinetics of assembled channels, but it is not yet clear where or how these subunits interact. Previous investigations of external access to the KCNE1 protein in assembled I(Ks) channels relied on occlusion of the pore by extracellular application of TEA(+), despite the very low TEA(+) sensitivity (estimated EC(50) > 100 mM) of channels encoded by coassembly of wild-type KCNQ1 with the wild type (WT) or a series of cysteine-mutated KCNE1 constructs. We have engineered a high affinity TEA(+) binding site into the h-KCNQ1 channel by either a single (V319Y) or double (K318I, V319Y) mutation, and retested it for pore-delimited access to specific sites on coassembled KCNE1 subunits. Coexpression of either KCNQ1 construct with WT KCNE1 in Chinese hamster ovary cells does not alter the TEA(+) sensitivity of the homomeric channels (IC(50) approximately 0.4 mM [TEA(+)](out)), providing evidence that KCNE1 coassembly does not markedly alter the structure of the outer pore of the KCNQ1 channel. Coexpression of a cysteine-substituted KCNE1 (F54C) with V319Y significantly increases the sensitivity of channels to external Cd(2+), but neither the extent of nor the kinetics of the onset of (or the recovery from) Cd(2+) block was affected by [TEA(+)](o) at 10x the IC(50) for channel block. These data strongly suggest that access of Cd(2+) to the cysteine-mutated site on KCNE1 is independent of pore occlusion caused by TEA(+) binding to the outer region of the KCNE1/V319Y pore, and that KCNE1 does not reside within the pore region of the assembled channels.

[A case of left renal cell carcinoma in a young male adult with left varicocele].

A 25-year-old man presented to our hospital with the chief complaint of left-sided painless scrotal swelling. Varicocele was diagnosed and high ligation was performed. Two months later, he noticed asymptomatic gross hematuria. Transabdominal ultrasonography and abdominal computed tomographic scanning showed a left renal tumor measuring more than 10 cm in diameter. Radical nephrectomy (thoraco-abdominal approach) was performed and pathological diagnosis was granular cell carcinoma (G2, pT2, INF alpha, pNX, pMX). He then received intramuscular injections of interferon-alpha 3 million units on three days per week. The frequency of renal cell carcinoma was reported to be about 1-3% for individuals in the 20s in the recent Japanese literature, and renal cell carcinoma in a young man with left varicocele is very rare.

Clinicopathological study of mucinous gastric carcinoma.

BACKGROUND AND AIMS: Mucinous gastric carcinoma (MUC) is relatively a rare subtype of gastric carcinoma, and there has been considerable controversiy over the prognosis of this type of carcinoma. In this study we tried to analyze the clinicopathological differences between MUC and other types of gastric carcinoma (non-MUC) and determine whether MUC is associated with a worse prognosis than non-MUC. MATERIAL AND METHODS: We reviewed 645 patients with pathologically confirmed gastric cancer who underwent gastrectomy in our facility during the period from 1975 through 1997. Among them, 20 patients (3.1%) had gastric carcinoma with (MUC), and 625 patients had it without extracellular mucin (non-MUC). In addition, we classified MUC into two groups (well-differentiated type; 7 cases and poorly differentiated type; 9 cases) and analyzed the differences between them. RESULTS: The MUC tumors were more often located in the lower and the upper third of the stomach (MUC: 55% and 25%, non-mUC: 41% and 18%, respectively). The patients with MUC had more serosal invasion (t3 plus t4; MUC: 45%, non-MUC: 18%), more-invasive carcinoma (Type 3 plus 4; MUC: 60%, non-MUC: 36%) and more lymph-node involvement (MUC: 45%, non-MUC: 38%) than the patients with non-MUC. The patients with MUC were more advanced in stage at the time of diagnosis (Stage III plus IV; MUC: 50%, non-MUC: 26%) and had a higher peritoneal dissemination rate (MUC: 30%, non-MUC: 12%) and a lower curability rate (MUC: 60%, non-MUC: 78%) than the patients with non-MUC. The mean size of tumors in MUC (7.4 cm) was larger than that of non-MUC (5.5 cm). Therefore, the overall 5-year survival rate for MUC patients (33%) was lower than that for non-MUC patients (64%). There were no significant differences between well-differentiated and poorly differentiated subtypes of MUC except for the curability and peritoneal dissemination rates. CONCLUSIONS: The overall survival rate for patients with MUC was worse than that for patients with non-MUC. The poor prognosis was correlated with more advanced stage at diagnosis and more frequent serosal invasion. These results suggest the need to diagnose patients with MUC in the early stage of cancer and that in the case of the advanced stage, wide excision of the surrounding tissues and aggressive lymph-node dissection will be needed.

[Psychogenic lower urinary tract dysfunction in women: patho-physiological investigation for psychogenic frequency-urgency syndrome and psychogenic urinary retention].

PURPOSE: Psychogenic lower urinary tract dysfunction (PLUTD) is composed of two syndromes; psychogenic frequency-urgency syndrome (PFUS) and psychogenic urinary retention (PUR). We evaluated the patho-physiology of PFUS and PUR, and explored the different pathogenesis in these syndromes. MATERIAL AND METHODS: Forty five patients with PLUTD, consisting of 23 patients with PFUS and 22 patients with PUR were investigated by using the psychological tests: CMI (Cornell Medical Index) and TEG (Todai's Egogram), a quantitative perspiration test in 45 females (23 patients with PFUS and 22 patients with PUR), and simultaneous measurements of voiding cysto-urethrography and urodynamic studies using the Life-Tech 6 channel polygraph in 35 patients (17 patients with PFUS and 18 patients with PUR). RESULTS: The prevalence in ages revealed two peaks, 20 years and 50 to 60 years. Over 25% of them had pyuria more than 10/hpf of WBC. Peak flow rate measured by uroflowmetry showed normal range in PFUS group and decreased in PUR group. The functional vesical volume was less than 100 ml in most patients with PFUS. Residual urine in PUR group was significantly greater. Capacity of the PFUS group were able to hold over 400 ml of contrast instilled through the urethral catheter, despite increased desire to void. Over 15% of the study group with PFUS showed uninhibited systolic contraction of detrusor (> 15 cm H2O) during filling phase. The measurement value of urodynamic parameters demonstrated that a periodic follow-up survey of the upper urinary tract should be performed because of the low compliance bladder in the patients with PLUTD. During voiding phase, the women with PFUS had a tendency to be divided into two groups, hypercontractile or acontractile detrusor. The voiding cysto-urethrography (VCUG) showed a tendency of bladder neck opening on patients with PFUS during filling phase. Most of PLUTD cases demonstrated a round to triangle shape on vesical configuration, which led to a spastic condition of detrusor muscle. We attempted to measure the quantitative perspiration using 3 kinds of loading tests; respiratory, arithmetic and psychological load. In the psychological loading test, we asked 98 questions about their daily lives including occupation, living condition, family relationship and sexual activities. Arithmetic loading test consisted of counting in reverse, subtraction and multiplication. The quantitative perspiration rate resulted in a "positive" in many patients with PFUS. Respiration loading test was performed to measure the respiration volume during 3 large inhales. Most patients with PUR tested within the normal range for respiration except for those patients with decreased or no perspiration during the psychiatric loading test. These results may reflect the psychological elements including suppression and subconscious defense mechanism. Neurosis which was diagnosed as having type III to type IV of the Cornell Medical Index was demonstrated in less than under 40% of patients with PFUS and more than 55% patients with PUR. There was no significant trend or difference between PFUS and PUR detected from Todai's Egogram. CONCLUSIONS: Due to the reflection of many psychological responses, it is necessary to investigate from various examinations including psychological, autonomical and classical urological studies for accurate diagnosis of PLUTD.

Effect of adenosine triphosphate on human coronary circulation.

We investigated in humans the effects of adenosine triphosphate (ATP), administered by intracoronary bolus (4-16 microg) or intravenous infusion (25-200 microg/kg/min), on coronary and systemic hemodynamics and electrocardiogram (ECG) variables. All patients had normal epicardial coronary arteries. The maximal coronary blood flow velocity (CBFV) was determined with intracoronary bolus of papaverine. A 12 microg bolus of ATP (n=12) caused maximal coronary hyperemia similar to that caused by papaverine. Intracoronary boluses caused a small brief decrease in arterial pressure but no significant changes in HR or ECG variables. Intravenous infusion of ATP at 150 microg/kg/min (n=15) caused a decrease in the coronary resistance index similar to that caused by papaverine, but the rate of increase in CBFV by ATP was smaller than that caused by papaverine. No patients had a significant change in ECG variables, but some patients (40%) had a serious decrease in arterial pressure. These studies suggest that maximal coronary vasodilation can be achieved safely with intracoronary ATP administration and that intravenous infusions at 150 microg/kg/min cause near-maximal coronary hyperemia in most patients.

[A case of renal oncocytoma associated with acquired cystic disease of the kidney].

We report a case of renal oncocytoma associated with acquired cystic disease of kidney (ACDK). A right renal mass was incidentally found on an annual ultrasonography of the kidneys in a 56-year-old female patient who had been on maintenance hemodialysis for 6 years. Computerized tomography (CT) showed a right hypervascular renal mass, suggesting a renal cell carcinoma associated with ACDK. Right radical nephrectomy was performed. The post-operative pathological diagnosis was renal oncocytoma. Renal oncocytoma in ACDK is very rare, and the pathological characteristics of oncocytoma are discussed.

[A case of spontaneous repair of the ureteral rupture caused by ureteral carcinoma].

We report a 47-year-old male patient with a spontaneous ureteral rupture caused by ureteral carcinoma. Drip infusion pyelography (DIP) and computerized tomography (CT) demonstrated the extravasation of contrast medium around the dilated upper ureter. Nephrostography showed the extinction of extravasation 4 days after the DIP. A total nephroureterectomy with the excision of a cuff of bladder was performed for the transitional cell carcinoma of the right lower ureter. Meticulous pathological examination of the specimen revealed discontinuity of the muscle layer, edema and fibrin deposition in the submucosal layers in the upper ureter indicating the site of the rupture. These findings suggest that the spontaneous rupture of the ureter caused by the ureteral carcinoma could be spontaneously repaired in a short period.

Effects of a novel, potent benzothiazepine Ca2+ channel antagonist, DTZ323, on guinea-pig ventricular myocytes.

The effects of a 1,5-benzothiazepine derivative, (+)-cis-3-(acetyloxy)-5-[2-[[2-(3,4-dimethoxyphenyl)ethyl]-methyla mino]ethyl]-2,3-dihydro-2-(4-methyoxyphenyl)-1,5-benzothiazepine-4 (5H)-one (DTZ323), on membrane currents were investigated in guinea-pig ventricular myocytes using the whole-cell patch-clamp technique. DTZ323 suppressed the L-type Ca2+ channel currents (I[Ca(L)]) more selectively than the T-type Ca2+ channel and the Na+ channel currents. DTZ323 inhibited I[Ca(L)] in a use- and a voltage-dependent manner with 24 times higher potency than that of diltiazem. Rate of recovery of I[Ca(L)] from the conditioned block by DTZ323 was faster compared with diltiazem and verapamil, and was steeply dependent on the holding potential at resting membrane potential range in ventricular myocytes (-90 to -60 mV). Our results suggest that DTZ323 is a selective Ca2+ channel antagonist, the most potent among the 1,5-benzothiazepine Ca2+ channel antagonists, and that the voltage- and use-dependent effect of DTZ323 on I[Ca(L)] is due to the steep voltage dependence of the rate of dissociation from the cardiac L-type Ca2+ channels.

1,5-benzothiazepine binding domain is located on the extracellular side of the cardiac L-type Ca2+ channel.

To determine whether 1,5-benzothiazepine Ca2+ channel blocker approaches its binding domain within the cardiac L-type Ca2+ channel from inside or outside of the membrane, we tested the effects of a novel potent 1,5-benzothiazepine derivative (DTZ323) and its quaternary ammonium derivative (DTZ417) on guinea pig ventricular myocytes by using the whole-cell patch-clamp technique. The extracellular application of DTZ417 suppressed the L-type Ca2+ channel currents (I[Ca(L)]) with an IC50 value of 1.2 +/- 0.02 microM, which was close to the IC50 value of diltiazem (0.63 +/- 0.01 microM). The suppression of I[Ca(L)] by DTZ417 was voltage and use dependent but lacked tonic block, which allowed us to investigate the onset of the effect on I[Ca(L)] by changing the holding potential (HP) from -90 to -50 mV in the presence of DTZ417. DTZ417 did not have significant effects on I[Ca(L)] at an HP of -90 mV. At -50 mV, DTZ417 (50 microM) applied from the extracellular side completely suppressed I[Ca(L)], whereas it had no effect from the intracellular side. DTZ323 (1 microM) also inhibited I[Ca(L)] only from the extracellular side, without any effects by the intracellular application of < or = 10 microM. However, a quaternary phenylalkylamine derivative, D890 (0.1 mM), acted only from the intracellular side. These results suggest that in contrast to the phenylalkylamine binding site, in cardiac myocytes the 1,5-benzothiazepine binding site is accessible from the extracellular side of the L-type Ca2+ channel.

Complications and reimplantation of penile implants.

BACKGROUND: Complications of penile prosthesis implants can be divided into surgical and mechanical failure. We investigated penile prosthesis implants to clarify the surgical and mechanical complications that have arisen in our clinical experience. METHODS: In the 11 years between 1984 and 1995, 83 penile prostheses were implanted in 74 patients ranging from 37 to 82 years of age. RESULTS: Of the 64 malleable and mechanical prostheses, 11 were extracted, including 4 removed because of surgical complications and 2 due to mechanical failure. Of the 19 inflatable prostheses, 6 were removed, including 1 extracted due to surgical complication and 5 extracted due to mechanical failure. Nine reimplantations for 8 patients were performed and all these cases had good results. As a result, 66 out of 74 patients could have coitus after prosthetic surgery. CONCLUSIONS: Penile prosthetic surgery is an established method of treating organic impotence, however, it should only be considered for selected and well-informed patients to avoid complications and revision surgery.

Diltiazem derivatives modulate the dihydropyridine-binding to intact rat ventricular myocytes.

To examine whether the modulation of the 1,4-dihydropyridine-binding by diltiazem derivatives, which has been shown in cardiac and skeletal muscle membranes, takes place in intact cardiac myocytes, effects of diltiazem on the specific binding of [3H](+)-PN200-110 to freshly isolated adult rat ventricular myocytes were investigated in normal Tyrode solution at 37 degrees C. Diltiazem consistently potentiated the [3H](+)-PN200-110-binding in a concentration-dependent manner, while DTZ323 (3-(acetyloxy)-5-[2-[[2- (3,4-dimethoxyphenyl)ethyl]-methylamino]ethyl]-2,3-dihydro-2(-4 methoxyphenyl)-1,5-benzothiazepin-4-(5H)-one), a potent diltiazem derivative, inhibited it in a non-competitive manner. In saturation studies, 100 microM decreased the Kd value of the 3[H](+)-PN200-110-binding (control, 0.102 +/- 0.008 vs. diltiazem, 0.074 +/- 0.004 (nM, n = 6), P < 0.05) without significant effect on Bmax (control, 65.7 +/- 6.4 vs. diltiazem, 76.7 +/- 4.4 (fmol/mg protein, n = 6). Moreover, membrane-impermeant quaternary diltiazem also potentiated the [3H](+)-PN200-110-binding in intact myocytes. These results suggest that diltiazem modulates the 1,4-dihydro-pyridine-binding even in intact cardiac myocytes, and the binding site of diltiazem is accessible from the extracellular side of the L-type Ca2+ channels.