Search results for "Calcium in biology"
showing 10 items of 65 documents
Changes in cytosolic calcium in response to noxious heat and their relationship to vanilloid receptors in rat dorsal root ganglion neurons.
2001
Heat transduction mechanisms in primary nociceptive afferents have been suggested to involve a vanilloid receptor channel with high calcium permeability. To characterize the changes in free cytosolic calcium evoked by noxious heat stimuli (< or =51 degrees C, 10s), we performed microfluorometric measurements in acutely dissociated small dorsal root ganglion neurons (< or =32.5 microm) of adult rats using the dye FURA-2. Only neurons that responded with a reversible increase in intracellular calcium to high potassium were evaluated. Heat-induced calcium transients (exceeding mean + 3S.D. of the temperature dependence of the dye) were found in 66 of 105 neurons. These transients increased non…
RELATIONSHIP BETWEEN THEOPHYLLINE UPTAKE AND INOTROPIC EFFECT IN THE GUINEA-PIG HEART
1974
1 The time course of the positive inotropic effect of theophylline was compared with the time course of the uptake and release of [(3)H]-theophylline in guinea-pig isolated, electrically driven hearts perfused by the Langendorff method.2 Formation of theophylline metabolites could not be detected under the experimental conditions used.3 Theophylline entered myocardial tissue very rapidly in two different phases. The first process (half-time 21 s) amounted to 93% and the second (half-time 5 min 50 s) to 7% of the total uptake. The development of the positive inotropic effect of theophylline was about four times faster than even the rapid component of the uptake of the drug into the myocardiu…
Activation of P2Y receptors by ATP and by its analogue, ADPbetaS, triggers two calcium signal pathways in the longitudinal muscle of mouse distal col…
2008
Our previous research showed that ATP and adenosine 5'-O-2-thiodiphosphate (ADPbetaS) induce contractile effects in the longitudinal muscle of mouse distal colon via activation of P2Y receptors which are not P2Y(1) or P2Y(12) subtypes. This study investigated the nature of the P2Y receptor subtype(s) and the mechanisms leading to the intracellular calcium concentration increase necessary to trigger muscular contraction. Motor responses of mouse colonic longitudinal muscle to P2Y receptor agonists were examined in vitro as changes in isometric tension. ATP or ADPbetaS induced muscular contraction, which was not affected by P2Y(11) or P2Y(13) selective antagonists. Calcium-free solution or th…
Investigations of the dual contractile/relaxant properties showed by antioquine in rat aorta.
1993
1. In the present study we assessed the activity of antioquine, a bisbenzyltetrahydroisoquinoline alkaloid isolated from Pseudoxandra sclerocarpa, by examining its effects on the contractile activity of rat isolated aorta, specific binding of [3H]-(+)-cis-diltiazem, [3H]-nitrendipine and [3H]-prazosin to cerebral cortical membranes and the different molecular forms of cyclic nucleotide phosphodiesterases (PDE) isolated from bovine aorta. 2. Contractions in rat aorta induced by high concentrations of KCl (80 mM) and noradrenaline (1 microM) were inhibited by antioquine in a concentration-dependent manner (0.1 microM- 300 microM). The alkaloid appeared more potent against KCl-induced contract…
Participation of Intracellular Calcium Stores in Serotonin-Induced Contractions in Rat Aorta
1993
Serotonin 1 mumol/l induces a contractile response in the isolated rat aorta in both the presence or absence of extracellular Ca. The present study analyzes the influence of temperature and caffeine on subsequent serotonin-induced contractions. In Ca-free medium, the contraction elicited by serotonin was higher at 25 degrees C than at 37 degrees C. In addition, the existence of two independent intracellular Ca pools releasable by serotonin, one of them also sensitive to caffeine, is postulated. The results also showed that addition of serotonin decreases the contractile response to this agonist in Ca-free medium.
Characterization of 5-hydroxytryptamine release from isolated rabbit and rat trachea: the role of neuroendocrine epithelial cells and mast cells
1995
Rabbit or rat isolated tracheae were incubated in vitro, and the release of 5-hydroxytryptamine (5-HT) and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) was determined by HPLC with electrochemical detection. Release of 5-HT from rabbit tracheae could be evoked by the calcium ionophore A 23187 and, in a calcium-dependent manner, by depolarizing concentrations of potassium (45 mmol/l), but not by the mast cell degranulating drug compound 48/80. High potassium- and A 23187-evoked release of 5-HT was markedly higher from tracheae of newborn compared to adult rabbits. In rabbit tracheae, mechanical removal of the mucosa resulted in 80-90% reduction in tissue 5-HT and in a similar reduction …
Effects of Dehydroepiandrosterone Sulfate on Cellular Calcium Responsiveness and Vascular Contractility
1995
Abstract Dehydroepiandrosterone sulfate (DHEAS) is an endogenous steroid having a wide variety of biological effects, but its physiological role remains undefined. Since an age-related decline of DHEAS corresponds to the progressive onset of atherosclerosis, cardiovascular diseases, and overall mortality, we investigated a possible protective role of DHEAS in vascular disease by studying the effects of this hormone (10 −7 to 10 −5 mol/L) on cytosolic free calcium and contractility in different in vitro vascular tissue preparations. DHEAS produced a significant, dose-dependent relaxation of isolated helical strips of rat tail artery precontracted with KCl (60 mmol/L) (89.7±18.7%, P <.01)…
In vitro tracheal hyperresponsiveness to muscarinic receptor stimulation by carbachol in a rat model of bleomycin-induced pulmonary fibrosis
2006
Summary 1 Bleomycin-induced lung injury is widely used as an experimental model to investigate the pathophysiology of pulmonary fibrosis but the alterations in the pharmacological responsiveness of airways isolated from bleomycin-exposed animals has been scarcely investigated. The aim of this study was to examine the in vitro tracheal responses to muscarinic receptor stimulation with carbachol in a rat bleomycin model. 2 Concentration–response curves to carbachol (10 nm to 0.1 mm) were obtained in tracheal rings isolated from Sprague–Dawley rats 14 days after endotracheal bleomycin or saline. The intracellular calcium signal in response to carbachol (10 μm) was measured by epifluorescence m…
Thimerosal induces calcium mobilization, fructose 2,6-bisphosphate synthesis and cytoplasmic alkalinization in rat thymus lymphocytes
1991
The effect of thimerosal on intracellular calcium ([Ca2+]i), pH (pHi) and fructose 2,6-bisphosphate (Fru 2,6-P2) in thymus lymphocytes was investigated. The effect of thimerosal on cell growth was also examined. Thimerosal produced a dose-dependent increase in [Ca2+]i, pHi and in the level of fructose 2,6-bisphosphate. Thimerosal was, however, unable to produce cell proliferation and inhibited [3H]thymidine incorporation when cells were challenged with PHA and costimulator. In the absence of external calcium, thimerosal produced only a slight increase in [Ca2+]i. In Na(+)-containing buffer, thimerosal induced an initial acidification (0.05 +/- 0.01 pH units), followed by an alkalinization o…
Increased calcium influx is responsible for the sustained mechanical tone in colon from dystrophic (mdx) mice
2001
Abstract Background & Aims: Proximal colon from dystrophic mice develops spontaneous tone increment, but the mechanisms involved in its development have not been investigated. This study examined whether alterations in the properties of cell membrane calcium channels and/or sarcoplasmic reticular (SR) Ca 2+ -adenosine triphosphatase (ATPase) contribute to tone development. Methods: Effects of calcium-free solution, nifedipine, pinaverium (calcium channel blockers), and cyclopiazonic acid (CPA; SR Ca 2+ -ATPase inhibitor) on the contractile activity of colon from mdx and control mice were determined. Results Calcium-free solution abolished spontaneous contractions in both preparations, but d…