Search results for "Calcium"
showing 10 items of 1740 documents
Endothelin-1-induced potentiation of adrenergic responses in the rabbit pulmonary artery: role of thromboxane A(2).
2001
Abstract To examine whether low concentrations of endothelin-1 potentiate the vasocontrictor response to adrenergic stimulation, we recorded the isometric response of rings of rabbit pulmonary artery to electrical stimulation and noradrenaline. Endothelin-1 (10 −10 M) potentiated the contractions induced by electrical stimulation and noradrenaline. The endothelin ET B receptor antagonist (2,6-dimethylpiperidinecarbonyl-γ-methyl-Leu- N in -[Methoxycarbonyl]- d -Trp- d -Nle) (BQ-788, 10 −6 M), but not the endothelin ET A receptor antagonist cyclo( d -Asp-Pro- d -Val-Leu- d -TRP) (BQ-123, 10 −6 M), inhibited the potentiating effects of endothelin-1. Pretreatment with the cyclooxygenase inhibit…
Differential effects of calcium channel antagonists (omega-conotoxin GVIA, nifedipine, verapamil) on the electrically-evoked release of [3H]acetylcho…
1990
Electrically-evoked release of [3H]acetylcholine from autonomic neurons (myenteric plexus), motoneurons (phrenic nerve) and the central nervous system (neocortex) was investigated in the presence and absence of the calcium channel antagonists omega-conotoxin GVIA, nifedipine and verapamil, whereby the same species (rat) was used in all experiments. Release of [3H]acetylcholine was measured after incubation of the tissue with [3H]choline. omega-Conotoxin GVIA markedly reduced (70%) the evoked release of [3H]acetylcholine from the myenteric plexus of the small intestine (IC50: 0.7 nmol/l) with a similar potency at 3 and 10 Hz stimulation. An increase in the extracellular calcium concentration…
Cardiac effects of isoliquiritigenin
1997
The effects of isoliquiritigenin on force of contraction (Fc), L-type Ca2+ current (I(Ca)) and intracellular Ca2+ concentration ([Ca2+]i) were investigated in rat ventricular heart muscle. Isoliquiritigenin increased Fc and I(Ca) and, after longer exposure times, resting tension and [Ca2+]i. The effect of isoliquiritigenin (100 microM) on I(Ca) was diminished by Rp-cAMPS (30 microM). 1H-[1,2,4]oxa- diazolo[4,3-a]quinoxalin-1-one (50 microM) did not influence the effects of isoliquiritigenin on Fc and I(Ca). The positive inotropic effects of isoprenaline and forskolin, but not of 3-isobutyl-1-methylxanthine, were potentiated by isoliquiritigenin (100 microM). In the presence of milrinone (10…
Inhibition by Fendiline of the Transient Outward Current in Rat Ventricular Cardiomyocytes
1999
The effects of fendiline on the transient outward current (Ito) were investigated in rat ventricular cardiomyocytes. Extracellularly applied fendiline reduced peak and steady-state current amplitude of Ito; the inactivation of Ito was accelerated by the drug, which reflects onset of block. The described effects were concentration dependent: half-maximal effects were achieved at approximately 3 microM fendiline. Intracellularly applied fendiline (3 microM) did not affect Ito within 5 min. The steady-state current amplitude of Ito was more efficiently suppressed by the drug at 22 +/- 1 degrees C than at 36 +/- 1 degrees C. The recovery of Ito was analyzed by the application of twin depolarizi…
Voltage-Dependent Effects of Barnidipine in Rat Vascular Smooth Muscle
2003
The effects of the dihydropyridine nifedipine and its more lipophilic congener, barnidipine, were investigated in smooth muscle preparations from the rat in resting and depolarizing conditions. Both drugs relaxed precontracted aortic rings more potently in depolarizing conditions, barnidipine being more potent than nifedipine. Currents through Ca 2+ channels in rat vascular smooth muscle cells (A7r5) and in isolated rat cardiomyocytes were reduced more potently by both drugs at a holding potential of-40 mV than at -80 mV. However, barnidipine and nifedipine were more effective in reducing the current in A7r5 cells than in cardiomyocytes. The IC 50 obtained in aortic rings and in A7r5 cells …
Comparison of prognostic usefulness (three years) of computed tomographic angiography versus 64-slice computed tomographic calcium scanner in subject…
2010
Coronary computerized tomographic angiography (CTA) has been used as a noninvasive method for ruling out high-grade stenoses. Even in the absence of such stenoses, analysis of coronary atherosclerosis may provide for important prognostic information, and this may be superior to exclusive coronary artery calcium scoring. We tested this hypothesis in patients undergoing CTA for clinical indications who had no stenoses requiring revascularization. From December 2004 to December 2006, 706 consecutive patients who underwent CTA but had no high-grade stenoses were included (58% men, mean age 59 ± 11 years). CTA and coronary artery calcium scoring (Agatston method) were performed using a 64-slice …
Evaluation by reverse phase HPLC of [3H]acetylcholine release evoked from the myenteric plexus of the rat.
1990
Myenteric plexus-longitudinal muscle strips isolated from the small intestine of rats were incubated with [3H]choline to measure the synthesis and the release of [3H]acetylcholine. To separate different radioactive compounds (acetylcholine, choline, phosphorylcholine) from both the tissue and the overflow a new method, the reverse phase HPLC, was used. The radiochromatogram following the injection of a [3H]choline-standard and a [14C]acetylcholine-standard onto the HPLC showed a clear separation of both isotopes with a recovery rate of roughly 100%. Incubation of the muscle strips with [3H]choline caused the synthesis of [3H]acetylcholine (30,000 dpm/preparation) that increased 2-fold, when…
Effects of physical training on metabolism of connective tissues in young mice.
1980
The effects of physical training on the metabolism of collagen, calcium and glycosaminoglycans in various connective tissues were studied in male NMRI mice. The mice to be trained and their controls were about 3 weeks old (expt. I) and 8 weeks old (expt. II) at the commencement of training. The training was performed on a 5 degree inclined treadmill 5 days a week for 4 weeks in expt. I and for 3 weeks in expt. II. The daily exercise time was progressively increased from 20 min in the first week up to 80 min in the third week. The incorporation of 3H-proline to collagen hydroxyproline was increased by training in long bones, skeletal muscle and Achilles tendon, whereas the incorporation of 3…
Depolarization-induced influx of sodium in response to phenylephrine in rat atrial heart muscle.
1991
1. The effects of alpha 1-adrenoceptor stimulation on transmembrane potential, currents and ion fluxes were investigated in multicellular preparations and/or single cells obtained from the left atrium of rat hearts. 2. In multicellular preparations, phenylephrine caused a concentration-dependent positive inotropic effect, an increase in action potential duration, and a decrease in resting potential; the effects were antagonized by phentolamine. 3. In the presence of phenylephrine (100 mumol/1), two levels of resting potential were observed when the preparations were, alternately, electrically stimulated or kept at rest (-74 +/- 1 mV during activity and -62 +/- 4 mV at rest; mean +/- S.E.M.;…
Presynaptic effects of scopolamine, oxotremorine, noradrenaline and morphine on [3H] acetylcholine release from the myenteric plexus at different sti…
1987
The inhibition by three modulators (oxotremorine, noradrenaline, morphine) of acetylcholine release from the myenteric plexus preincubated with [3H]choline was investigated at different stimulation frequencies and calcium concentrations. Moreover, [3H]acetylcholine release evoked by a low (0.1 Hz) or a high (10 Hz) stimulation rate was investigated at different calcium concentrations either in the absence or presence of scopolamine. A reduced calcium concentration (0.6 mmol/l) inhibited acetylcholine release more at 0.1 Hz (74% +/- 3%) than at 10 Hz (44% +/- 8%). Scopolamine enhanced the stimulated acetylcholine release at a calcium concentration of 1.8 mmol/l. At calcium concentrations hig…