[Health belief model and attendance at screenings for gastric cancer in a population in Miyagi, Japan]

The relationship between frequency of attendance at the screening programs for gastric cancer and Health Belief Model (HBM) variables was studied in a convenient sample (n = 337) of residents in a town of Miyagi prefecture, Japan. Frequency of attendance at the screening within the past five years was determined from records of the Miyagi Cancer Society, which provided an annual screening program for gastric cancer for study subjects. Using a self-administered questionnaire with 12 questions, with responses measured on a 5-point Likert scale, the five variables of HBM (health motivation, perceived susceptibility and seriousness of gastric cancer, perceived benefit and barriers to participating in the screening) were constructed. Health motivation (r = 0.14, p < 0.01), susceptibility (r = 0.16, p < 0.01), and benefit (r = 0.20, p < 0.001) correlated positively with frequency of attendance at the screening, whereas seriousness (r = -0.20, p < 0.001) and barriers (r = -0.40, p < 0.001) correlated negatively. Multiple regression analysis, which included five variables of HBM, three modifying variables (sex, age, family history of gastric cancer), and four personality scales measured by the short-scale Eysenck Personality Questionnaire-Revised, demonstrated that barriers to participating in the screening (beta = 0.35, p < 0.001) and family history of gastric cancer (beta = 0.17, p < 0.01) were significantly associated with frequency (R = 0.4994, F = 6.203, p < 0.001). Path analysis was conducted to explore the relationship between frequency, HBM, personality, and other modifying variables.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood clearance and tissue distribution of various formulations of alpha-tocopherol injection after intravenous administration

The in vivo elimination and tissue distribution (2 h after administration) of various types of formulations of alpha-tocopherol as a model drug were examined in rats. An organic cosolvents formulation of alpha-tocopherol (alpha-tocopherol/EtOH/polyethylene glycol 400) was rapidly removed from the blood circulation, the ratio of the distributed alpha-tocopherol was 20% in the lungs, about 70% in the liver and about 10% in the spleen. The main reason for this was considered to be the appearance of droplets more than 10 microns in diameter in the blood. Elimination of the micelle formulation using Brij58 from the blood was the most rapid, followed by Tween80 and HCO60. This order is thought to be due to the difference in the polyoxyethylene group among these surfactants. In liposome formulations, liposomes having a diameter of about 80 nm were the most stable in the blood circulation, and alpha-tocopherol was distributed in the reticuloendothelial system (RES) in the smallest ratio. The uptake of liposomes by the spleen and lungs depended on the liposome size. The uptake by the liver was in the decreasing order of 28 nm >> 42 nm, 151 nm, 195 nm, 3656 nm > 106 nm > 75 nm. The 100 nm lipid emulsion was eliminated from the blood more rapidly than the 100 nm liposome formulation.

Cardiovascular effects of OPC-13340, a potent, long-acting 1,4-dihydropyridine calcium channel blocker, in dogs

The cardiovascular effects of OPC-13340, a newly developed 1,4-dihydropyridine calcium channel blocker, were examined in several canine preparations. In conscious normotensive and DOCA-salt hypertensive dogs, OPC-13340, at doses of 10 to 30 micrograms/kg, i.v., and 0.3 to 3 mg/kg, p.o., exerted an hypotensive action in a dose-dependent manner. The hypotensive action of OPC-13340 was longer lasting and more potent than that of nicardipine and nifedipine. In conscious, normotensive instrumented dogs, OPC-13340, at doses of 1 and 3 mg/kg, p.o., dose-dependently decreased total peripheral resistance and mean blood pressure and increased heart rate, cardiac output and left ventricular contractility. In anesthetized open-chest dogs, OPC-13340, at doses of 1 to 30 micrograms/kg, i.v., increased coronary blood flow and decreased mean blood pressure, heart rate, coronary vascular resistance, arteriovenous oxygen difference and myocardial oxygen consumption. In contrast to OPC-13340, nicardipine did not change the myocardial oxygen consumption. From these results it was concluded that OPC-13340 lowered blood pressure and improved coronary circulation in dogs and that the duration of these actions was longer lasting than that of nifedipine and nicardipine. These actions of OPC-13340 may be useful in the treatment of hypertension and angina pectoris.

Novel positive inotropic agents: synthesis and biological activities of 6-(3-amino-2-hydroxypropoxy)-2(1H)-quinolinone derivatives

A series of 6-(3-amino-2-hydroxypropoxy)-2(1H)-quinolinones has been synthesized and evaluated for positive inotropic activity on the canine heart. Some of these derivatives have a potent activity with none or negative chronotropic effect in isolated, blood-perfused dog heart preparations. They also display a high selectivity for positive inotropic effect over chronotropic and vasodilatory effects in anesthetized dogs. (+/-)-6-[2-Hydroxy-3-[(3-methoxybenzyl)amino]propoxy]-2(1H)-quinolinone (39) and (+/-)-6-[3-(3,4-dimethoxybenzyl)amino]-2-hydroxypropoxy]-2 (1H)-quinolinone (40) were further investigated in conscious dogs. After iv administration, they did not affect heart rate or mean blood pressure at the dose producing a 50% increase in the peak of the first derivative of the left ventricular pressure. The compounds (39, OPC-18750, and 40, OPC-18790) are the most promising agents with desirable biological activities, and now are currently undergoing clinical evaluation.

[Serum concentrations of ranitidine after intravenous administration in geriatric patients under general anesthesia]

The elimination rate of serum ranitidine was investigated in healthy geriatric patients under general anesthesia. The patients (50-90 y.o., ASA classification 1 and 2) were divided into Group 1 (age greater than or equal to 70, n = 9) and Group 2 (50 less than age less than 65, n = 6). Ranitidine (1 mg.kg-1) was administered intravenously after the induction of anesthesia, and the serum concentration was measured at 60 min and 120 min. The biological half life of serum ranitidine in Group 1 was 98.9 +/- 13.8 (M +/- SD) min, which was not significantly different from that of Group 2. The half life correlated with intraoperative urine volume (r = 0.62), but not with intraoperative bleeding or age. The duration of the above effective ranitidine concentration was calculated as about 4 and half hours after its i.v. injection. This indicates that additional administration is necessary for longer operations.

[Studies on the erythrocyte membrane skeleton in a patient with chorea-acanthocytosis--theoretical speculation on the mechanism of neurological involvement]

Patients with chorea-acanthocytosis exhibit symptoms of self-biting, choreic movement, and acanthocytosis, but not dementia. The mechanism of choreic movements is still unknown. In order to clarify the etiologic mechanism underlying these movements, we evaluated the erythrocyte membrane in one patient with chorea-acanthocytosis. A 35-year-old female was admitted to Saitama Medical School Hospital because of involuntary movements. She was alert, well-oriented, and had no gross memory defects. She had slurred speech, choreic movements and lip biting. Laboratory examination showed acanthocytes in her peripheral red blood cells, normal serum lipid values, and caudate atrophy on her brain CT scan. In analyzing the acanthocytes, we initially evaluated the size of the acanthocyte population by incubating her red blood cells with plasma. The cell population approximately doubled after 2 hours incubation. Next we examined the protein composition of erythrocyte ghost by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). There was no significant difference between the patient's erythrocyte ghosts and those of a control. Then we investigated morphological changes in the patient's erythrocyte by scanning and transmission electron microscopy (SEM and TEM). SEM showed the typical acanthocyte shape. The quick-freeze, freeze-substitution method confirmed that the routine TEM section was not artifactual, and was in fact in accurate reflection of the actual features of acanthocytes. TEM of the sections prepared from erythrocyte ghosts demonstrated that spectrin tended to be accumulated in the thorn region. Furthermore, TEM of quick-freeze, deep-etched replica of the ghost revealed more clearly a spectrin network densely packed on the inner hydrophilic surface.(ABSTRACT TRUNCATED AT 250 WORDS)

Complete disappearance of metastatic abdominal tumors from gastric cancer after treatment with irsogladine maleate

A 60-year-old woman with gastric cancer had undergone partial gastrectomy in September 1989. Pathological examination revealed a poorly differentiated adenocarcinoma of pT3pN3pM0 (not resected for cure), stage IV. Postoperative adjuvant therapy comprised 1-(tetrahydro-2-furanyl)-5-fluorouracil plus uracil and OK-432. On 11 August 1990, two forefinger-tip-sized tumors were palpated beneath the operation scar. They increase in size, the superior tumor reaching 4x3 cm, the inferior tumor 5x3 cm on 5 September. Then, on 17 September, the inferior tumor was resected but the superior tumor remained; the histological type was poorly differentiated adenocarcinoma. After the operation, from 20 September, she was given 4 mg irsogladine maleate orally every day. On 8 October, there was no increase in the size of the superior tumor. By 29 October, the superior tumor had disappeared and no further tumor appeared thereafter; the patient showed no sign of relapse.

[Altered bone metabolism in db/db mice]

Bone and calcium metabolism was investigated in genetically obese, diabetic db/db mice and compared with that in a new hypoglycemic agent (AS-6) treated db/db mice and in their lean litter mates as controls. The 5-week-old db/db mice (serum Ca 9.88 +/- 0.22 mg/dl, glucose 258.6 +/- 13.3 mg/dl) were randomly divided into two groups. One group, together with their lean litter mates, was fed a commercial diet (CE-2). The other db/db group was fed CE-2 diet containing 0.1% of AS-6. Both groups were fed for 20 weeks. The serum glucose and calcium levels in db/db control groups (serum Ca 12.3 +/- 0.1 mg/dl, glucose 650.2 +/- 23.9 mg/dl) were higher than those in lean control groups (Ca 9.8 +/- 0.2 mg/dl, glucose 180.7 +/- 10.1 mg/dl). The wet, dry and ashed weights of the femur in db/db control were significantly lower and the length of femur in db/db control was significantly shorter than those of lean controls. These data suggest that retarded bone growth in db/db mice is related to progression of diabetes. Although, there was no change in Ca/P, Ca/ash and total perimeter in femurs, the cortical area in the femurs of db/db control mice (0.65 +/- 0.02 mm2) was significantly smaller than that of the femurs of lean control mice (0.74 +/- 0.02 mm2). The cortical bone thinning observed in the db/db control could have been caused by increased bone resorption. Treatment with AS-6 for 20 weeks resulted in a 48.6% decrease of serum glucose and 5.2% decrease of calcium as compared with db/db controls.(ABSTRACT TRUNCATED AT 250 WORDS)

[Amnesic effect of oral midazolam as premedication in children]

We evaluated the sedative and amnesic effects of oral midazolam as premedication in children. Sixteen children, aged 4-12 yr, undergoing elective minor surgery were divided into 2 groups. One group received midazolam 0.5 mg.kg-1 with atropine 0.03 mg.kg-1 orally. The other control group received only atropine 0.03 mg.kg-1. There was no significant difference in the sedative scale at induction between the 2 groups. Doll-recall was used to assess the amnesic effects. In the midazolam group, 75% of the children forgot dolls they had seen on entering the operating room. Midazolam produced significant anterograde amnesia but no retrograde amnesia. This result suggests that children who received midazolam as premedication forget unpleasant memories at induction and their postoperative emotional responses are least influenced by their memories. We conclude that oral midazolam 0.5 mg.kg-1 is an effective preanesthetic medication in children.

[A new preoperative evaluation of platelet aggregation--Part II]

With the new platelet function test which we reported in the first paper, the platelet aggregation was evaluated in 50 patients, and the comparison with the results of bleeding time was made in 20 cases. There was no statistical correlation between the bleeding time and the platelet aggregation. The bleeding time has been considered as an indicator of platelet function and is included in a preoperative check list. However, its result depends on the amount of platelets and the endothelial factor, and the reliability of bleeding time on platelet function is considered small, especially in patients medicated with antiplatelet drugs. For such patients, the platelet aggregation test is essential. The present study demonstrated that the patient belonging to grade-1 were resistant to hemostasis during the operation. Taking into the surgical and anesthetic depression on the platelet function into consideration, the patients below grade-2 are risky for the surgery.

Persistence of individual dendritic spines in living brain slices

A number of theories on the cellular basis of learning and memory propose that long-term changes in synaptic strength are encoded by changes in the properties of dendritic spines. Such theories imply that individual spines retain their identity over time. Using a new technique for fluorescent labelling of synaptic structures together with confocal microscopy, we have found that the appearance of individual spines on viable cells remains unchanged over observations periods of up to 5 hours. Even in slices exposed to kainic acid at concentrations that abolished synaptic transmission, groups of spines remained identifiable on cells clearly damaged by the toxin. The robust persistence of individual spines demonstrated here establishes an essential prerequisite for their potential role as mnemonic elements.

Cardiovascular actions of OPC-18790: a novel positive inotropic agent with little chronotropic action

OPC-18790 [(+/-)-6-[3-(3,4-dimethoxybenzylamino)-2-hydroxypropoxy]- 2(1H)-quinolinone], a novel positive inotropic agent, was investigated in several in vitro and in vivo experiments to elucidate its cardiovascular effects and its mechanism of action. In isolated blood-perfused dog heart preparations, OPC-18790 increased contractile force at 10 to 1,000 nmol i.a.; increased coronary arterial blood flow at 30 to 1,000 nmol; and decreased sinus rate slightly at 1,000 nmol. Atrio-ventricular nodal conduction was slightly facilitated with OPC-18790 (10 to 1,000 nmol), whereas ventricular automaticity tended to decrease. OPC-18790 (10(-6) to 10(-4) M) increased contractile force in isolated ventricular muscles of dogs, cats, rabbits and guinea pigs but not rats. OPC-18790 increased left ventricular contractile force dose-dependently in anesthetized open-chest dogs and in conscious dogs with slight or no changes in heart rate and blood pressure. The positive inotropic effect of OPC-18790 was not affected by beta-blockade. OPC-18790 (10(-5) to 10(-4) M) prolonged the duration of action potential in guinea pig papillary muscles. Na+, K(+)-ATPase was not inhibited, but peak-III phosphodiesterase (low Km cyclic AMP specific fraction, inhibited by cyclic GMP) was inhibited by OPC-18790 (IC50 = 0.41 x 10(-6) M) in dog myocardium. However, such an inhibitory action of phosphodiesterase can hardly be reconciled with the lack of a positive chronotropic effect shown by OPC-18790. Thus, these results suggest that OPC-18790 may have an additional mechanism. The cardiovascular effects revealed by this study suggest that OPC-18790 may exert a beneficial effect in the treatment of congestive heart failure.

Characterization of a novel aquaretic agent, OPC-31260, as an orally effective, nonpeptide vasopressin V2 receptor antagonist

1. OPC-31260, a benzazepine derivative, has been studied for its ability to antagonize the binding of arginine vasopressin (AVP) to receptors in rat liver (V1) and kidney (V2) plasma membranes, for antagonism of the antidiuretic action of AVP in alcohol-anaesthetized rats and for diuretic action in conscious normal rats. 2. OPC-31260 caused a competitive displacement of [3H]-AVP binding to both V1 and V2 receptors with IC50 values of 1.2 +/- 0.2 x 10(-6) M and 1.4 +/- 0.2 x 10(-8) M, respectively. 3. OPC-31260 at doses of 10 to 100 micrograms kg-1, i.v., inhibited the antidiuretic action of exogenously administered AVP in water-loaded, alcohol-anaesthetized rats in a dose-dependent manner. OPC-31260 did not exert an antidiuretic activity suggesting that it is not a partial V2 receptor agonist. 4. After oral administration at doses of 1 to 30 mg kg-1 in normal conscious rats, OPC-31260 dose-dependently increased urine flow and decreased urine osmolality. The diuretic action of OPC-31260 was characterized as aquaresis, the mode of diuretic action being different from previously known diuretic agents such as furosemide, hydrochlorothiazide and spironolactone. 5. The results indicate that OPC-31260 is a selective V2 receptor antagonist and behaves as an aquaretic agent. OPC-31260 will be a useful tool in studying the physiological role of AVP and in the treatment of various conditions characterized by water retention.

Inhibitory reflex during bronchoconstrictions induced by histamine and Ascaris suum antigen

We investigated the involvements of sympathetic and nonadrenergic nervous systems in the inhibitory reflex following bronchoconstriction in dogs. Inhalations of a 0.00125% solution of histamine and Ascaris suum antigen (3 mg protein) to the bronchial side induced reflex tracheal constriction following bronchoconstriction. An intra-arterial infusion of 5 micrograms/min of atropine to the tracheal site changed the reflex tracheal constrictions by histamine and antigen inhalations into tracheal dilatations. The reflex tracheal dilatations were abolished by the combination of intra-arterial propranolol (100 micrograms) and transections of both the bilateral superior laryngeal nerves and the spinal cord at the C1 level. The reflex tracheal constrictions induced by histamine and antigen inhalations were increased with 100 micrograms propranolol. Furthermore, the reflex tracheal constrictions were enhanced by the combination of 100 micrograms propranolol and transection of the spinal cord. These findings indicate that during the constriction of the bronchial smooth muscle, not only a reflex tracheal constriction mechanism but also one of reflex dilatation operates and that the latter reflex response may be mainly mediated by the sympathetic nerves, with partial involvement of the nonadrenergic nerves. This inhibitory reflex may attenuate asthmatic bronchoconstriction.

[Clinical studies of panipenem/betamipron in pediatrics]

We conducted clinical studies on panipenem/betamipron (PAPM/BP), a newly developed parenteral carbapenem antibiotic, for its clinical application in the field of pediatrics. 1. A clinical study was performed on 13 children with infections, including 6 with acute bronchopneumonia, 1 each with acute pharyngitis, acute bronchitis, sepsis, staphylococcal scalded skin syndrome, urinary tract infection, subcutaneous abscess and furuncle. PAPM/BP was administered by intravenous drip infusion. Doses varied from 12 to 27 mg/kg body weight were given t.i.d. or q.i.d. Lengths of treatment ranged from 4 to 25 days. Clinical efficacies were excellent in 3 and good in 9 cases, with an efficacy rate of 92%. 2. No adverse reactions were observed. In laboratory tests, elevations of GOT, GPT and urobilinogen were observed in 3 cases. It was concluded that PAPM/BP was a promising drug for the treatment of bacterial infections in children.

[A new method for preoperative evaluation of platelet aggregation: Part I]

Newly introduced antiplatelet drugs such as ticlopidine or cilostazol are often administered to preoperative patients. However, how to evaluate the effect of these drugs on anesthetic management remains unsettled. The platelet aggregation test was performed on 20 operative patients, and the aggregation patterns are classified into five categories. The platelet aggregation is almost unchanged in some patients, and slightly depressed in others. The new classification of platelet aggregation patterns that we introduced for preoperative evaluation seems to be a good indicator of platelet function in patients medicated with antiplatelet drugs.

Chemotactic activities of peripheral blood polymorphonuclear leukocytes and peritoneal exudate polymorphonuclear leukocytes in MRL mice

Chemotactic responsiveness to fMet-Leu-Phe in concentrations of 10(-8) to 10(-4) M in the Boyden chamber was compared between peritoneal exudate cells (PEC) and polymorphonuclear leukocytes (PMN) isolated from peripheral blood, between MRL/Mp-+/+ (MRL-+/+) and MRL/Mp-lpr/lpr (MRL-lpr/lpr) mice, and between young (6-9 week old) and aged (16-24 week old) mice. Chemotactic responsiveness of PEC did not differ between MRL-+/+ and MRL-lpr/lpr, and young and aged mice. While, PMN showed greater chemotaxis in aged MRL-+/+ mice than that in aged MRL-lpr/lpr mice. These results suggest that chemotactic responsiveness of PMN differ from that of PEC which is assumed to be preactivated by an inflammatory agent injected into the peritoneal cavity to elicit cells. Less responsiveness of PMN to the bacterial origin peptide might relate to the autoimmune disease of this murine model.

Negative Corona Current Pulses and Cathode Sheath Instabilities in a Short Point-Plane Gap in CO2

Waveforms ofthe first negative corona current pulses have been measured in C02 and C02+SF6 mixtures as a function of applied voltage and gas pressure in the range 6�67-66�7 kPa. A complex form of the pulses with a step on the pulse leading edge and a current hump on the pulse trailing part has been found at gas pressures below 40 kPa. Changing the cathode surface material from copper to copper iodide, which has an exceptionally high photoelectric yield, resulted in at least a twofold increase in height of the step on the pulse leading edge, but had little effect on the main current rise to the pulse peak. The use of unconditioned cathodes resulted in the appearance of peculiar current spikes on the pulse tail, which are tentatively attributed to positive-streamer-like instabilities of the cathode sheath. The implications of these results for theories of Trichel pulse formation are discussed, and a physical picture of the phenomenon based on the presumed existence of a cathode-directed streamer associated with the steep pulse rise is outlined.

[Platelet aggregation during hypotensive anesthesia using prostaglandin E1]

We studied platelet aggregation during hypotensive anesthesia using prostaglandin E1 (PGE1) on 22 patients (6 males, 16 female). All the patients underwent operations on head, neck, abdomen, breast, or lower extremities under general anesthesia. They had no history of hematological disease or taking drugs which affected platelet aggregation. The blood was sampled three times under a constant condition of anesthesia with intravenous drip: firstly, before using PGE1, secondly, under hypotensive state during PGE1 infusion at the speed of 0.05-0.3 micrograms.kg-1.min-1, and thirdly, after cessation of PGE1, after the blood pressure had recovered to the level before PGE1 infusion. ADP, collagen and epinephrine were added to the platelet rich plasma as clumping agents; their final concentrations were 0.3 microM, 2 micrograms.ml-1, and 2 micrograms.ml-1 respectively. The aggregating curves were recorded for 7 min. There were no significant differences in platelet aggregation among the three blood samples; neither in platelet count nor in bleeding time. Bleeding did not seem to have increased due to PGE1 infusion. These results suggest that PGE1 at hypotensive dose could be used safely under general anesthesia regarding hemostasis.

[Studies on operative method in intestinal hemodynamics of panperitonitis]

Using a tissue spectrum analyser, intestinal hemodynamics were determined in 85 patients with panperitonitis. By the preoperative shock score(ss) the patients were classified into group I (ss less than or equal to 1: n = 30), group II (2 less than or equal to ss less than or equal to 4: n = 30), group III (5 less than or equal to ss: n = 25). The index of hemoglobin concentration (IHb) was increased in group II, while the index of oxygen saturation (ISO2) was decreased in groups I and II. There was an increase of the cardiac index and a decrease of total peripheral resistance in group III compared with other groups, indicating a hyperdynamic state. Oxygen delivery and consumption showed no marked changes in groups I and II, but they were impaired in group III. The incidence rate of anastomotic leakage was 0% in group I, 37.5% in group II, and 100% in group III. It was considered that in the group II patients, a decrease in tissue oxygenation caused by stagnation of blood flow becomes a cause of anastomotic leakage. In the group III patients, tissue damage caused by marked disturbances of oxygen delivery and consumption leads to a high incidence of anastomotic leakage. I concluded that the second look operation should be performed for the patients with the disturbance of oxygen delivery and consumption.

Activated T lymphocyte subsets in experimental allergic neuritis

Changes in activated T cell subsets in peripheral blood were examined during the course of experimental allergic neuritis (EAN), using two-color immunofluorescence flow cytometry. Both CD4+ and CD8+ activated T cells decreased transiently before the onset of clinical signs, and increased just around the time of onset of the disease. In contrast, during the recovery phase, the numbers of CD4+ activated T cells returned to the normal range, whereas CD8+ activated T cells continued to increase. These findings imply that activation of CD4+ helper/inducer cells contributes mainly to the evolution of EAN, and that of CD8+ suppressor cells are necessary for recovery.

Effects of dietary glucose or fructose on the secretion rate and particle size of triglyceride-rich lipoproteins in Zucker fatty rats

Effects of dietary carbohydrate on the secretion rate and particle size of triglyceride-rich lipoproteins were examined in Zucker fatty rats fed fructose and glucose and were compared with those of Zucker lean rats. Carbohydrates were supplied as 10% drinking solutions for 14 days. As compared with lean rats, Zucker fatty rats had hyperinsulinemia and hypertriglyceridemia associated with an increased rate of triglyceride secretion into the circulation. Feeding fructose and glucose to fatty rats produced an increase in plasma glucose levels, whereas plasma insulin concentrations did not show significant changes. Neither fructose nor glucose supplementation produced significant changes in the rate of triglyceride secretion. Despite this, plasma triglyceride concentrations in fructose-fed fatty rats were twice as high as those in glucose-fed rats or those receiving no supplementary carbohydrate. Particle diameters of lipoproteins of density between 0.96 and 1.006 were larger in fructose-fed fatty rats than in those receiving no sugar. The results suggest that feeding fructose, but not glucose, into fatty rats is associated with an impairment of triglyceride removal and a resultant increase in plasma triglyceride concentration, the latter of which is accompanied by an increase in triglyceride contents in each particle.

Subcellular mechanism of the positive inotropic effect of a new quinolinone derivative OPC-8490 on the dog ventricular myocardium

OPC-8490 [3,4-dihydro-6-[4-(4-oxo-4-phenylbutyl)-1- piperazinylcarbonyl]-2(1H)-quinolinone citrate] elicited a positive inotropic effect in a concentration-dependent manner on the isolated dog ventricular trabeculae electrically driven at 0.5 Hz in Krebs-Henseleit solution bubbled with 95% O2-5% CO2 at 37 degrees C. The beta-adrenoceptor antagonist, bupranolol (3 x 10(-7) mol/l), did not influence the effect of OPC-8490. The maximal effect of OPC-8490 was 0.19 compared with isoproterenol (1.0). The time course of the increase in contractile force coincided with that of the concomitant cyclic AMP accumulation induced by OPC-8490. The concentration-response curve for the OPC-8490-induced increase in contractile force was superimposable on that of the elevation of cyclic AMP levels. OPC-8490 (10(-5) mol/l) shifted the concentration-response curve for isoproterenol to the left and upward. These results imply that the accumulation of cyclic AMP induced by OPC-8490 through an inhibition of peak III PDE may be responsible for its positive inotropic effect. However, the OPC-8490-induced increase in the contractile force was not abolished by carbachol (3 x 10(-6) mol/l) when the cyclic AMP accumulation caused by the compound was completely inhibited by carbachol. In addition, OPC-8490 did cause a change in the time course of isometric contractions characteristic of cyclic AMP accumulation. These findings indicate that both the cyclic AMP-dependent (peak III PDE inhibition) and the cyclic AMP-independent mechanisms (prolongation of action potential duration by inhibition of K+ conductance) may be involved in the positive inotropic effect of OPC-8490 on the dog ventricular muscle.