RESUMEN
The utility of intravenous prochlorperazine (PCZ) in the treatment of nausea, vomiting, and headache may be limited by the akathisia that occurs frequently with the recommended 2-min infusion rate. We tested the hypothesis that decreasing the rate of PCZ infusion to 15 min reduces the incidence of akathisia at 1 hour. This double-blinded, randomized, controlled trial was conducted in the Emergency Department of an academic tertiary-care medical center with an annual census of 95,000 emergency patient visits. We enrolled a convenience sample of adult patients who received 10 mg i.v. PCZ for the treatment of nausea, vomiting, or headache. Subjects were randomized to receive either a 2-min infusion of PCZ (10 mg) followed by a 15-min infusion of saline, or a 2-min infusion of saline followed by a 15-min infusion of prochlorperazine. The incidence of akathisia at 1 hour was measured by using explicit diagnostic criteria. One hundred sixty patients were randomly enrolled into two groups, which were comparable with respect to age, gender, weight, and complaint. Akathisia developed in 31 of 84 patients (36.9%) who received the 2-min infusion of PCZ and in 18 of 76 patients (23.7%) who received the 15-min infusion of PCZ (p = 0.07), a 36% (95% CI, -5% to 61%) relative reduction. The delta from pre-infusion to postinfusion scores between the two groups was not significant (p = 0.19). We conclude that slowing the rate of PCZ infusion does not decrease akathisia.
Asunto(s)
Acatisia Inducida por Medicamentos/prevención & control , Antieméticos/administración & dosificación , Proclorperazina/administración & dosificación , Adolescente , Adulto , Anciano , Antieméticos/efectos adversos , Método Doble Ciego , Femenino , Humanos , Infusiones Intravenosas/métodos , Masculino , Persona de Mediana Edad , Proclorperazina/efectos adversos , Estudios Prospectivos , Estadísticas no ParamétricasRESUMEN
Rate and equilibrium measurements of ryanodine binding to terminal cysternae fractions of heavy sarcoplasmic reticulum vesicles demonstrate that its activation by high concentrations of monovalent salts is based on neither elevated osmolarity nor ionic strength. The effect of the ions specifically depends on their chemical nature following the Hofmeister ion series for cations (Li+ < NH+4 < K- approximately Cs+
Asunto(s)
Aniones/farmacología , Cationes Monovalentes/farmacología , Músculo Esquelético/metabolismo , Canal Liberador de Calcio Receptor de Rianodina/metabolismo , Rianodina/metabolismo , Retículo Sarcoplasmático/metabolismo , Nucleótidos de Adenina/farmacología , Animales , Técnicas In Vitro , Cinética , Músculo Esquelético/efectos de los fármacos , Concentración Osmolar , Conejos , Retículo Sarcoplasmático/efectos de los fármacosRESUMEN
Biosynthetic transport from the trans-Golgi network (TGN) to the plasma membrane (PM) is mediated by secretory vesicles. We analyzed secretory vesicle transport in real time using a GFP-tagged secretory protein, hCgB-GFP, consisting of human chromogranin B (hCgB) and green fluorescent protein (GFP). The fusion protein was expressed transiently in Vero cells or in a stable clone after induction with butyrate. After arrest of the biosynthetic protein transport at 20 degrees C, fluorescent hCgB-GFP colocalized with TGN38, a marker of the TGN. Subsequent release of the secretion block at 37 degrees C led to the formation of green fluorescent vesicles. Confocal analysis revealed that these vesicles were devoid of TGN38 and of Texas Red-coupled transferrin and cathepsin D, markers of the endosomal/lysosomal pathway. As determined by fluorometry and metabolic labelling hCgB-GFP was secreted from the TGN to the PM with a t(1/2) of 20-30 minutes. Video-microscope analysis of green fluorescent vesicles showed brief periods of rapid directed movement with maximal velocities of 1 microm/second. Vesicle movement occurred in all directions, centrifugal, centripetal and circumferential, and 50% of the vesicles analyzed reversed their direction of movement at least once within an observation period of 45 seconds. In the presence of nocodazole the movement of fluorescent vesicles ceased. Concomitantly, secretion of hCgB-GFP was slowed but not completely blocked. We suggest that microtubules (MT) facilitate the delivery of secretory vesicles to the PM by a stochastic transport, thereby increasing the probability for a vesicle/target membrane encounter.
Asunto(s)
Gránulos Citoplasmáticos/fisiología , Microtúbulos/fisiología , Animales , Transporte Biológico Activo/efectos de los fármacos , Membrana Celular/fisiología , Chlorocebus aethiops , Cromograninas/metabolismo , Endosomas/fisiología , Aparato de Golgi/fisiología , Proteínas Fluorescentes Verdes , Humanos , Proteínas Luminiscentes/metabolismo , Lisosomas/fisiología , Microtúbulos/efectos de los fármacos , Movimiento , Nocodazol/farmacología , Proteínas Recombinantes de Fusión/metabolismo , Células VeroRESUMEN
Both calcium and caffeine induced calcium release from actively loaded heavy sarcoplasmic reticulum vesicles were studied to analyze the dependence of both activities on the composition of the release medium with respect to monovalent anions. Calcium is unable to induce net calcium release while caffeine remains effective as releasing agent when the experimental media contain neither chloride nor nitrate ions. Caffeine induced calcium release is not suppressed by chelating residual medium calcium (approximately 0.5-1 microM) with 2 mM EGTA added 15 s prior to 10 mM caffeine. Calcium release from vesicles loaded in media containing 0.2 M gluconate as monovalent anion is induced when the medium is supplemented with chloride or nitrate. The release amplitude increases linearly when K-gluconate is replaced by KCl. At constant ionic strength the release amplitude becomes maximal at a chloride concentration of 0.2 M. The chloride effect completely disappears when 2 mM EGTA are added simultaneously. When chloride is replaced by nitrate, as releasing agent, maximal release is achieved already by addition of 0.1 M K-nitrate. The releasing effect of nitrate can only partially be suppressed by EGTA. The different effectiveness of gluconate, chloride and nitrate as calcium release supporting ions corresponds to their activating effect on the binding of ryanodine to the calcium release channel in the vesicular membranes.
Asunto(s)
Cafeína/farmacología , Calcio/metabolismo , Cloruros/farmacología , Nitratos/farmacología , Retículo Sarcoplasmático/metabolismo , Animales , Aniones , Calcio/farmacología , Fraccionamiento Celular , Ácido Edético/farmacología , Cinética , Músculos/metabolismo , Conejos , Rianodina/farmacología , Retículo Sarcoplasmático/efectos de los fármacos , Retículo Sarcoplasmático/ultraestructuraRESUMEN
The effect of ATP on the calcium release channel in heavy sarcoplasmic reticulum vesicles modulated by ryanodine has been analyzed by monitoring active calcium uptake and caffeine induced calcium release under near physiological conditions. Native as well as ryanodine reacted vesicles display a complex time course of calcium uptake resulting in nearly complete exhaustion of medium calcium when ATP in combination with an ATP-regenerating system, in contrast to ATP alone, or dinitrophenyl phosphate, were used to support calcium uptake. Applying of dinitrophenyl phosphate as energy yielding substrate, not affecting channel activity, allowed to estimate the fraction of light vesicles devoided of calcium channels contaminating the heavy preparation as the fraction that stores calcium after the preparation has been treated with channel opening, low concentrations of ryanodine (1 microM). Calcium uptake by contaminant light vesicles (25%) cannot account for calcium storage, as well as, abolition of caffeine induced calcium release of ryanodine treated heavy vesicles. Calcium uptake of native and ryanodine treated vesicles is accompanied by the uptake of equivalent amounts of inorganic phosphate arising from ATP hydrolysis indicating that calcium is mainly stored as calcium phosphate. The momentary capability of the preparation to accumulate calcium was measured by activating calcium uptake during the calcium storage period with 0.2 mM 45CaCl2 and 4 mM phosphate at short time intervals. A significant increase of the momentary uptake activity with time was observed being more pronounced for ryanodine treated than for native vesicles indicating that under regenerating conditions, ATP can induce closing of the native and even more effectively of the ryanodine modified calcium release channels.
Asunto(s)
Cafeína/farmacología , Calcio/farmacología , Rianodina/farmacología , Retículo Sarcoplasmático/metabolismo , Adenosina Trifosfato/metabolismo , Animales , Fraccionamiento Celular/métodos , Cinética , Músculos/metabolismo , Conejos , Retículo Sarcoplasmático/efectos de los fármacosRESUMEN
The inhibition by ryanodine of caffeine induced calcium release from actively loaded heavy sarcoplasmic vesicles has been studied in order to analyse the relation between the occupancy of the vesicular calcium release channels by ryanodine and channel function. Ryanodine binding was monitored with [3H]ryanodine under ionic conditions favouring the establishment of binding equilibrium. Binding follows 1:1 stoichiometry yielding dissociations constants between 7-12 nM and 12-15 pmol ryanodine/mg vesicular protein as maximum number of ryanodine binding sites. When ryanodine labeling was monitored by measuring the decline of the amplitude of caffeine induced calcium release 50% inhibition occurred at a free ryanodine concentration of 1 nM. At this concentration less than 10% of the available ryanodine binding sites are occupied. Caffeine induced calcium release is completely abolished when 3 pmol ryanodine/mg have reacted. A corresponding divergence between ryanodine binding and its effect on caffeine induced calcium release was observed when the initial rate of ryanodine binding was measured either by labeling the vesicles with [3H]ryanodine or by following the decline with time of caffeine induced calcium release. Caffeine induced calcium release declines four times faster than the fraction of unoccupied ryanodine binding sites, k = 4.3 x 10(4) M-1 s-1 versus 1.2 x 10(4) M-1 s-1. The observed interrelation between the occupation of ryanodine binding sites and its effect on caffeine induced calcium release indicates that the caffeine sensitive calcium channel functions as an assembly of at least 4 ryanodine binding sites whereby the occupation of one site suffices to abolish calcium release. The stoichiometric composition appears to be not fixed but might change according to the size of the fraction of ryanodine receptors exhibiting caffeine sensitivity. The reported data were evaluated according to the algorithm derived by H. Asai and M. F. Morales, J. Biol. Chem. 4, 830-838 (1965) for the activity of a macromolecule and the extent of an inhibiting reaction.
Asunto(s)
Cafeína/farmacología , Calcio/metabolismo , Músculos/metabolismo , Orgánulos/metabolismo , Receptores Colinérgicos/metabolismo , Rianodina/metabolismo , Retículo Sarcoplasmático/metabolismo , Animales , Cinética , Músculos/ultraestructura , Orgánulos/efectos de los fármacos , Conejos , Receptores Colinérgicos/efectos de los fármacos , Canal Liberador de Calcio Receptor de Rianodina , Retículo Sarcoplasmático/ultraestructuraRESUMEN
Mops, used as a proton buffer, specifically enhances the accumulation of calcium or strontium by light sarcoplasmic reticulum vesicles driven by ATP or dinitrophenylphosphate as energy-yielding substrates when calcium-precipitating agents are absent. The enhancement of ion uptake by Mops is much greater for strontium than for calcium and is further increased when potassium is replaced by sodium as the dominant monovalent cation. Mops affects neither the activity of the calcium- or strontium-activated transport enzyme nor the active accumulation of calcium in the presence of oxalate, i.e. when the pump runs unidirectionally forward. Passive calcium and strontium efflux rates of approximately 40-50 nmol.mg-1.min-1 are considerably reduced when histidine/glycerophosphate or Tris/maleate are exchanged for Mops. The observed passive efflux rates and their modulation by Mops are too small, in relation to the rate of ion influx, to account for either the relatively small calcium and strontium load in the absence of precipitating agents or for its modulation by Mops. The results imply that the pump itself mediates ion efflux dependent on pump activity and the different degree of saturation of lumenal ion-binding sites by calcium and strontium, as well as their susceptibility to Mops.
Asunto(s)
Calcio/metabolismo , Morfolinas , Retículo Sarcoplasmático/metabolismo , Adenosina Trifosfato/metabolismo , Animales , Transporte Biológico Activo , ATPasas Transportadoras de Calcio/metabolismo , Dinitrofenoles/metabolismo , Membranas Intracelulares/metabolismo , Luz , Conejos , Estroncio/metabolismoRESUMEN
Heavy sarcoplasmic reticulum vesicles isolated from rabbit skeletal muscle were reacted in high ionic strength solutions with ryanodine. The effect of this reaction on ATP - and dinitrophenyl phosphate supported calcium uptake and caffeine induced calcium release were studied. At pH 7.0 calcium uptake and caffeine induced calcium release are simultaneous affected by the occupation of 0.5 pmol ryanodine binding sites/mg protein, having an affinity of 0.33 nM-1.
Asunto(s)
Alcaloides/metabolismo , Calcio/metabolismo , Rianodina/metabolismo , Retículo Sarcoplasmático/metabolismo , Animales , Humanos , Rianodina/farmacología , Retículo Sarcoplasmático/efectos de los fármacosRESUMEN
Heavy sarcoplasmic reticulum vesicles were reacted with ryanodine in 0.6 M KCl 0.3 M sucrose at pH 6.3 and pH 7.0 at 20 degrees C. The inhibition of caffeine induced calcium release from actively loaded vesicles by ryanodine was applied to monitor time course and attainment of equilibrium of the interaction of ryanodine with its receptors in the vesicular membranes. At ryanodine concentrations rising from 0.1-100 microM, the logarithms of the release amplitudes linearly decline with time. The dependence of the inactivation reaction on the concentration of ryanodine did not saturate in the applicable concentration range. The reaction halflife times are concentration dependent. At pH 7.0, the half times decline from 100 to 10 s when the ryanodine concentration is raised from 0.1 to 1 microM. At pH 6.3 a corresponding decline occurs between 3 microM and 100 microM. The marked dependence of the inactivation reaction on medium pH requires reaction times of one and five hours at pH 7.0 and 6.3, respectively for the attainment of reaction equilibrium at low ryanodine concentrations. The dependence of the amplitude of calcium release on the concentration of added ryanodine has been evaluated as proposed by Gutfreund (Enzymes: Physical Principles, p. 71, Wiley-Interscience, London 1972) for the preparation's affinity for ryanodine and its number of binding sites. At pH 7.0, preparations appear to contain only 0.7 pmol sites per mg protein having an affinity for ryanodine of 0.33 nM-1. The titration curves for caffeine induced calcium release, initial calcium uptake and final calcium level are identical, indicating that the three functions are controlled by the same receptor. Calcium induced calcium release, however, is only partially and differently affected by the occupancy of the high affinity ryanodine binding sites.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Alcaloides/farmacología , Calcio/metabolismo , Rianodina/farmacología , Retículo Sarcoplasmático/metabolismo , Animales , Cafeína/farmacología , Radioisótopos de Calcio , Ácido Egtácico/farmacología , Cinética , Músculos/metabolismo , Conejos , Retículo Sarcoplasmático/efectos de los fármacosRESUMEN
The occupancy of high-affinity ryanodine-binding sites of isolated heavy sarcoplasmic reticulum vesicles occurring in concentrated salt solutions affects ATP-dependent calcium accumulation and caffeine-induced calcium release. The initial suppression of calcium uptake is followed by a marked uptake activation resulting in a reduction of the final calcium level in the medium. Simultaneously, caffeine-induced calcium release is blocked. The dependence of inhibition of calcium uptake and caffeine-induced calcium release observed in assay media containing physiological concentrations of magnesium and ATP on the concentration of ryanodine corresponds to the drug's effectiveness in living muscles.
Asunto(s)
Alcaloides/farmacología , Calcio/metabolismo , Rianodina/farmacología , Retículo Sarcoplasmático/metabolismo , Adenosina Trifosfato/farmacología , Animales , Transporte Biológico Activo/efectos de los fármacos , Cafeína/farmacología , Músculos/metabolismo , Conejos , Retículo Sarcoplasmático/efectos de los fármacosRESUMEN
The blockage of all thiol residues accessible to the mercurial mersalyl in the sarcoplasmic reticulum membranes resulting in complete inactivation of the membranes' calcium transport system does interfere neither with caffeine- nor calcium-induced calcium release from actively loaded membrane vesicles.
Asunto(s)
ATPasas Transportadoras de Calcio/metabolismo , Calcio/metabolismo , Retículo Sarcoplasmático/metabolismo , Adenosina Trifosfato/metabolismo , Animales , Cafeína/farmacología , Calcimicina/farmacología , Ácido Egtácico/farmacología , Cinética , Músculos/metabolismo , ConejosRESUMEN
The ability of calcium loaded heavy sarcoplasmic reticulum vesicles to specifically respond to the addition of various agents such as caffeine, calcium ions and calmodulin antagonists to rapidly released calcium can largely be diminished by passing the vesicular suspension it 0.3 M sucrose, 0.6 M KCl, 4 mM CaCl2, pH 7.0 through a Sepharose 6B column or by centrifuging it through a sucrose gradient prepared with the same salt medium. Inactivation of calcium release does neither interfere with calcium uptake nor with the unspecific releasing effect caused by the application of high concentrations of calmodulin antagonists.
Asunto(s)
Calcio/metabolismo , Retículo Sarcoplasmático/metabolismo , Animales , Cafeína/farmacología , Calmodulina/antagonistas & inhibidores , Ácido Egtácico/farmacología , Imidazoles/farmacología , Cinética , Músculos/metabolismo , Inhibidores de Proteasas/farmacología , Conejos , Retículo Sarcoplasmático/efectos de los fármacos , Trifluoperazina/farmacología , p-Metoxi-N-metilfenetilamina/farmacologíaRESUMEN
The properties of the sarcoplasmic reticulum membranes isolated from slow-twitch type I soleus and fast-twitch type II psoas muscles of control and thyroxine treated rabbits were comparatively studied. Membrane yield, maximal calcium storing capacity, ATP-supported calcium uptake, calcium-dependent ATPase activity and calcium-dependent phosphoprotein formation were found to be 3-10 fold higher in psoas than in soleus preparations. Membrane yield, calcium-dependent ATPase activity, ATP-supported calcium transport and calcium-dependent phosphoprotein are at least twice enhanced in the membranes from soleus muscles of animals treated for 14-21 days with thyroxine. The corresponding capacities of the membranes from psoas muscles are not further augmented by the same thyroxine treatment. The maximal calcium storing capacity of the psoas membranes is their sole specific property which is significantly increased. The changes in the properties of the soleus muscles' sarcoplasmic reticulum membranes are engendered by an increase from 5 to 30-50% in the number of type II fibres. Since the calcium transporting properties of the sarcoplasmic reticulum membranes from type II fibres qualitatively differ from those of type I fibres, thyroxine does not only affect quantitative but also qualitative parameters of the muscles' sarcoplasmic reticulum membrane system.
Asunto(s)
Músculos/ultraestructura , Retículo Sarcoplasmático/efectos de los fármacos , Tiroxina/farmacología , Adenosina Trifosfatasas/metabolismo , Animales , Peso Corporal/efectos de los fármacos , Calcio/metabolismo , Electroforesis en Gel de Poliacrilamida , Histocitoquímica , Masculino , Músculos/efectos de los fármacos , Fosfoproteínas/biosíntesis , Conejos , Fracciones Subcelulares/metabolismo , Hormonas Tiroideas/sangre , Factores de TiempoRESUMEN
The decline of the transport ratio of the sarcoplasmic calcium pump observed in a recent study (A. Gafni and P. D. Boyer, Proc. Natl. Acad. Sci. USA 82, 89-101 [1985] ) results from the retardation of calcium oxalate precipitation at low calcium/protein ratios. The prevailing high internal calcium level supports a rapid calcium backflux and a compensatory ATP hydrolysis during net calcium uptake which reduces the transport ratio. Yet, the determined calcium backflux does not fully account for the decline of the transport ratio. A supposed modulation of the stoichiometry of the pump by external calcium (0.1 microM) is at variance with results of previous studies showing a constant transport ratio of two in the same calcium concentration range.
Asunto(s)
Calcio/metabolismo , Retículo Sarcoplasmático/metabolismo , Adenosina Trifosfatasas/metabolismo , Adenosina Trifosfato/metabolismo , Animales , Transporte Biológico Activo , Fenómenos Químicos , Química Física , Técnicas In Vitro , Canales Iónicos/metabolismoRESUMEN
Under adequate experimental conditions calmodulin antagonists like compound 48/80 do not dissociate calcium uptake from the calcium-dependent ATP hydrolysis of skeletal muscle sarcoplasmic reticulum membranes but simultaneously inhibit both processes. Apart from the agent's pump inhibiting effect, they interact with the caffeine sensitive calcium channel in the sarcoplasmic reticulum causing a rapid transient calcium release.
Asunto(s)
ATPasas Transportadoras de Calcio/antagonistas & inhibidores , Calcio/metabolismo , Calmodulina/fisiología , Retículo Sarcoplasmático/enzimología , Cafeína/farmacología , Radioisótopos de Calcio , Técnicas In Vitro , Oxalatos/farmacología , Ácido Oxálico , Fosforilación , p-Metoxi-N-metilfenetilamina/farmacologíaRESUMEN
Vanadate binding to sarcoplasmic reticulum vesicles results in the loss of the externally located high affinity calcium binding sites of the calcium transport ATPase. Conversely the occupation by calcium of the internally located low affinity sites in the vanadate enzyme complex leads to the release of vanadate. Since the total number of calcium binding sites is not diminished by vanadate binding but slightly increases we conclude that vanadate binding induces a transition of the enzymes external high to internal low affinity calcium binding sites. The transposition of external to internal calcium binding sites is accompanied by a definite change in the structure of the sarcoplasmic reticulum membranes. On vanadate binding the asymmetrically arranged electron dense protein particles become symmetrically distributed.
Asunto(s)
ATPasas Transportadoras de Calcio/metabolismo , Calcio/metabolismo , Retículo Sarcoplasmático/efectos de los fármacos , Vanadio/metabolismo , Animales , Sitios de Unión/efectos de los fármacos , Calcimicina/farmacología , Microscopía Electrónica , Conejos , Retículo Sarcoplasmático/enzimología , Retículo Sarcoplasmático/ultraestructura , VanadatosRESUMEN
The calcium-transport ATPase of the sarcoplasmic reticulum membranes is irreversibly inactivated by the combined action of Lasolocid and Triton X-100 at concentrations which separately do not interfere with the enzyme's activity. In the presence of Lasolocid the enzyme is most susceptible to inactivation when the Triton X-100 concentration just exceeds its critical micellar concentration, approximately, 0.2 mg X ml-1. Lasolocid becomes effective at a concentration of 10 microM and produces rapid inactivation at 100 microM. Phosphoprotein formation is less affected than phosphate liberation. The influence of the ATPase protein on the fluorescence intensity of Lasolocid passes a distinct maximum at the most effective Triton X-100 concentration of 0.2 mg X ml-1.
Asunto(s)
Adenosina Trifosfatasas/antagonistas & inhibidores , Calcio/metabolismo , Lasalocido/farmacología , Polietilenglicoles/farmacología , Retículo Sarcoplasmático/enzimología , Transporte Biológico/efectos de los fármacos , Hidrólisis , Técnicas In Vitro , Octoxinol , Espectrometría de FluorescenciaRESUMEN
The calcium-transport-ATPase of the sarcoplasmic reticulum membranes is irreversibly inactivated by the combined action of Lasolocid and Triton X-100 at concentrations which separately do not interfere with the enzyme's activity. In the presence of Lasolocid the enzyme is most susceptible to inactivation when the Triton X-100 concentration just exceeds its critical micellar concentration, approximately 0.2 mg . ml-1. Lasolocid becomes effective at a concentration of 10 microM and produces rapid inactivation at 100 microM. The enzyme is more rapidly inactivated in the active than in the inactive state.
Asunto(s)
ATPasas Transportadoras de Calcio/antagonistas & inhibidores , Detergentes/farmacología , Lasalocido/farmacología , Polietilenglicoles/farmacología , Retículo Sarcoplasmático/enzimología , Tensoactivos/farmacología , Animales , Cinética , OctoxinolRESUMEN
The activity of the calcium transport systems in the sarcoplasmic reticulum membranes operating in the forward and reverse modes depends on the presence of magnesium ions. When the system operates as an NTP-driven calcium pump, magnesium enters the reaction chain chelated with NTP. Magnesium is a component of the NDP-sensitive phosphoprotein species involved in the NDP-NTP exchange reaction. When the system operates in the reverse mode as a calcium efflux-driven NDP synthetase, magnesium together with inorganic phosphate rapidly forms the initial phosphorylated intermediate. The stability of the magnesium-phosphoprotein complex is considerably enhanced by an existing calcium gradient. Magnesium as well as calcium affects the partitioning of the energy in the reaction sequence.
Asunto(s)
Calcio/metabolismo , Canales Iónicos/fisiología , Magnesio/fisiología , Retículo Sarcoplasmático/metabolismo , Adenosina Difosfato/fisiología , Adenosina Trifosfato/fisiología , Transporte Biológico Activo , Proteínas de Unión al Calcio/fisiología , ATPasas Transportadoras de Calcio/fisiología , Humanos , Magnesio/metabolismoRESUMEN
The labeling of the protein moiety of the sarcoplasmic calcium transport ATPase by fluorescamine suppresses calcium transport, calcium dependent ATPase activity, protein phosphorylation by [gamma-32P]ATP and [32P]phosphate at different extent of amino group substitution. For the hydrolysis of para nitrophenylphosphate by the calcium transport ATPase, it is shown that the relationship between the extent of amino group labelling can considerably be altered by the temperature and the presence of ethyleneglycol. It is shown that the amino residues of the phosphatidylethanolamine moiety do not contribute to the inhibiting effect of fluorescamine labelling. The observations suggest that the different functions of the calcium transport system are based on the cooperation of a varying number of calcium transport ATPase molecules.