Swelling-activated chloride currents in embryonic chick heart cells.
(49/831)
AIM: To characterize a swelling-activated chloride current, I(Cl, swell), in white Leghorn chick heart cells and the effects of chlorpromazine (CPZ) effects. METHODS: The patch-clamp technique in the whole-cell configuration was used. RESULTS: Hyposmotic swelling elicited I(Cl, swell) in white Leghorn chick heart cells. The current amplitude increased from (452 +/- 200) pA to (849 +/- 373) pA with a reduction of osmolarity from 300 mmol.L-1 to 270 mmol.L-1, 4',4-Diisothiocyanostilbene-2,2'-disulphonic acid (DIDS) 100 mumol.L-1 decreased I(Cl, swell) from (1196 +/- 505) pA to (830 +/- 328) pA in hyposmotic solution. In white Leghorn chick heart cells I(Cl, swell) was not induced by CPZ 30 mumol.L-1, which is different from the case of E coli spheroplast. CONCLUSION: Swelling-activated chloride current was activated by hyposmotic swelling in white Leghorn chick heart cells. The mechanism for activating the current is different from that of mechanosensitive ion channels of E coli. (+info)
Acridine and phenothiazine derivatives as pharmacotherapeutics for prion disease.
(50/831)
Prion diseases in humans and animals are invariably fatal. Prions are composed of a disease-causing isoform (PrP(Sc)) of the normal host prion protein (PrP(C)) and replicate by stimulating the conversion of PrP(C) into nascent PrP(Sc). We report here that tricyclic derivatives of acridine and phenothiazine exhibit half-maximal inhibition of PrP(Sc) formation at effective concentrations (EC(50)) between 0.3 microM and 3 microM in cultured cells chronically infected with prions. The EC(50) for chlorpromazine was 3 microM, whereas quinacrine was 10 times more potent. A variety of 9-substituted, acridine-based analogues of quinacrine were synthesized, which demonstrated variable antiprion potencies similar to those of chlorpromazine and emphasized the importance of the side chain in mediating the inhibition of PrP(Sc) formation. Thus, our studies show that tricyclic compounds with an aliphatic side chain at the middle ring moiety constitute a new class of antiprion reagents. Because quinacrine and chlorpromazine have been used in humans for many years as antimalarial and antipsychotic drugs, respectively, and are known to pass the blood-brain barrier, we suggest that they are immediate candidates for the treatment of Creutzfeldt-Jakob disease and other prion diseases. (+info)
In vitro and in vivo protein phosphorylation in Avena sativa L. coleoptiles: effects of Ca2+, calmodulin antagonists, and auxin.
(51/831)
In vitro and in vivo protein phosphorylations in oat (Avena sativa L.) coleoptile segments were analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis and by two-dimensional gel electrophoresis. In vitro phosphorylation of several polypeptides was distinctly promoted at 1 to 15 micromolar free Ca2+ concentrations. Ca2(+)-stimulated phosphorylation was markedly reduced by trifluoperazine, chlorpromazine, and naphthalene sulfonamide (W7). Two polypeptides were phosphorylated both under in vitro and in vivo conditions, but the patterns of phosphorylation of several other polypeptides were different under the two conditions indicating that the in vivo phosphorylation pattern of proteins is not truly reflected by in vitro phosphorylation studies. Trifluoperazine, W7, or ethylene glycol-bis-(beta-aminoethyl ether)-N,N'-tetraacetic acid (EGTA) + calcium ionophore A23187 treatments resulted in reduced levels of in vivo protein phosphorylation of both control and auxin-treated coleoptile segments. Analysis by two-dimensional electrophoresis following in vivo phosphorylation revealed auxin-dependent changes of certain polypeptides. A general inhibition of phosphorylation by calmodulin antagonists suggested that both control and auxin-treated coleoptiles exhibited Ca2+, and calmodulin-dependent protein phosphorylation in vivo. (+info)
Phospholipase C activation by anesthetics decreases membrane-cytoskeleton adhesion.
(52/831)
Many different amphiphilic compounds cause an increase in the fluid-phase endocytosis rates of cells in parallel with a decrease in membrane-cytoskeleton adhesion. These compounds, however, do not share a common chemical structure, which leaves the mechanism and even site of action unknown. One possible mechanism of action is through an alteration of inositol lipid metabolism by modifying the cytoplasmic surface of the plasma membrane bilayer. By comparing permeable amphiphilic amines used as local anesthetics with their impermeable analogs, we find that access to the cytoplasmic surface is necessary to increase endocytosis rate and decrease membrane-cytoskeleton adhesion. In parallel, we find that the level of phosphatidylinositol 4,5-bisphosphate (PIP(2)) in the plasma membrane is decreased and cytoplasmic Ca(2+) is increased only by permeable amines. The time course of both the decrease in plasma membrane PIP(2) and the rise in Ca(2+) parallels the decrease in cytoskeleton-membrane adhesion. Inositol labeling shows that phosphatidylinositol-4-phosphate levels are increased by the permeable anesthetics, indicating that lipid turnover is increased. Consistent with previous observations, phospholipase C (PLC) inhibitors block anesthetic effects on the PIP(2) and cytoplasmic Ca(2+) levels, as well as the drop in adhesion. Therefore, we suggest that PLC activity is increased by amine anesthetics at the cytoplasmic surface of the plasma membrane, which results in a decrease in membrane-cytoskeleton adhesion. (+info)
Relationship of symptomatology, gender, and antipsychotic drug treatment with plasma homovanillic acid in schizophrenia.
(53/831)
AIM: To study the role of dopamine neurotransmission in schizophrenia and its drug treatment by assessing the relationship of plasma homovanillic acid (pHVA), a major central dopamine metabolite to various clinical parameters in schizophrenic patients. METHODS: pHVA was measured by high-performance liquid chromatography with electrochemical detection in a large cohort of both medicated and unmedicated DSM-IV schizophrenic patients. Prior to the measurement of pHVA, the patients were rated on the schedule for the assessment of positive and negative symptoms (PANSS). RESULTS: (1) pHVA in 46 patients receiving antipsychotic drugs was decreased, and in 58 drug-free patients increased, (7.4+/-2.7) microg/L and (10+/-4) microg/L compared with a matched control group (9 microg/L+/-3 microg/L, n=62) (ANOVA F=8.57, df=2, P < 0.01), respectively. Within the drug-free group, pHVA was higher in the patients with a more negative symptom profile. (2) No significant correlation of pHVA with overall SAPS or SANS scores was apparent in the drug-free patients, although within the SANS subscales, a significant relationships to anhedonia-asociality (r=0.32, P < 0.05) was apparent. The male drug-free patients showed a positive correlation of pHVA with negative symptoms (r=0.42, P < 0.05) while females showed no significant relationship with any PANSS subscales. CONCLUSION: The results suggest that an increased dopaminergic metabolism is apparent in (male) schizophrenic patients with predominantly negative symptoms, supporting reports that this change in neuronal activity may be related to the neuropathological abnormalities seen in the disease, which may differ between males and females. Such neuronal deficits of developmental origin may thus result in an elevation/disinhibition of central dopamine metabolism in schizophrenia. (+info)
Selective modulation of P-glycoprotein-mediated drug resistance.
(54/831)
Multidrug resistance associated with the overexpression of the multidrug transporter P-glycoprotein is a serious impediment to successful cancer treatment. We found that verapamil reversed resistance of CEM/VLB(100) cells to vinblastine and fluorescein-colchicine, but not to colchicine. Chlorpromazine reversed resistance to vinblastine but not to fluorescein-colchicine, and it increased resistance to colchicine. Initial influx rates of fluorescein-colchicine were similar in resistant and parental cells, whereas vinblastine uptake was about 10-fold lower in the resistant cells. These results provide indirect evidence that fluorescein-colchicine is transported from the inner leaflet of the membrane and vinblastine from the outer membrane leaflet. Verapamil inhibited fluorescein-colchicine transport in inside-out vesicles made from resistant cells, whilst chlorpromazine was found to activate the transport of fluorescein-colchicine. The chlorpromazine-induced activation of fluorescein-colchicine transport was temperature-dependent and may reflect its interaction with phospholipids localised in the same bilayer leaflet. Conversely, chlorpromazine localisation in this leaflet may be responsible for its allosteric inhibition of vinblastine transport from the opposing membrane leaflet. The proposed relationship between the selectivity of modulation of P-glycoprotein and the membrane localisation of the cytotoxic drug substrates and modulators may have important implications in the rational design of regimes for the circumvention of multidrug resistance clinically. (+info)
Differential effects of chlorpromazine on two vasoconstrictor tones in the rat.
(55/831)
Hindquarter compensator tone (HCT) is referred to as the sympathetic vasoconstrictor tone to the hindquarters of the rat induced by such hypotensive interventions as pentobarbital anesthesia, nitrate administration and blood loss. The aim of this study is to observe whether chlorpromazine (CPZ) injected intravenously in rats (0.5 mg/kg) inhibits the following two different kinds of vasoconstrictor tone: HCT induced by pentobarbital and the renal tone which is normally present in the conscious state. Rats were implanted with an electromagnetic flow probe around the terminal aorta or the left renal artery. The right common carotid was cannulated for mean arterial pressure (AP). Regional peripheral resistance (hind-quarter resistance [HQR] or renal resistance [RR]) was calculated as AP divided by regional flow. In rats under pentobarbital anesthesia, after CPZ, ganglionic blockade with hexamethonium bromide (25 mg/kg) did not decrease HQR. However, in conscious rats after CPZ, blockade decreased RR significantly. These findings indicate that CPZ inhibits HCT almost completely but scarcely decreases the renal tone and further suggest that HCT and the renal tone are generated by different mechanisms. (+info)
A kinetic method for the determination of nitrite by its catalytic effect on the oxidation of chlorpromazine with nitric acid.
(56/831)
A catalytic spectrophotometric method for the determination of trace amounts of nitrite is proposed. In acidic solution, chlorpromazine (CP) is oxidized by nitric acid to form a red compound, which is further oxidized to a colorless compound. The reaction is accelerated by trace amounts of nitrite and can be followed by measuring the absorbance at 525 nm: nitrite ion is regenerated and multiplied by nitric acid. The absorbance of the reaction increased with an increase in the reaction time, reached a maximum and decreased rapidly. Since the time required for the absorbance to reach the maximum decreased with increasing nitrite concentration, this value was used as the measured parameter for the nitrite determination. Under the optimum experimental conditions (2.3 M nitric acid, 1.2 x 10(-5) M CP, 40 degrees C), nitrite can be determined in the range 0-100 microg l(-1). The relative standard deviations (n = 6) are 4.7 and 1.8% for 40 and 100 microg l(-1) nitrite, respectively. The detection limit of this method (3sigma) is 1.2 microg l(-1). This method was successfully applied to a determination of nitrite in natural water samples. (+info)