The kinetics of calcium binding to fura‐2 and indo‐1

Jackson, Andrew P.; Timmerman, Michelle; Bagshaw, Clive R.; Ashley, Christopher

doi:10.1016/0014-5793(87)80752-4

Cited by 125 publications

(80 citation statements)

References 11 publications

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“…To our knowledge, A major finding of our study is that the decay of the fluorescence transients continues throughout diastole and that a variety of pharmacologic and physiologic maneuvers that alter contractile force produces parallel changes in -1) is at least an order of magnitude faster than the decay of the fluorescence transients we observe (24).…”

Section: Discussionmentioning

confidence: 82%

Cytosolic calcium transients from the beating mammalian heart.

Lee

Smith

Mohabir

et al. 1987

Proc. Natl. Acad. Sci. U.S.A.

134

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To elucidate the role of cytosolic calcium, [Ca2+]1, in the physiology of the normal and ischemic heart, we have developed a method for recording [Ca2+]1 transients from the epicardial surface of the rabbit ventricle after arterial perfusion with the cell-permeant cytosolic calcium indicator indo-l AM. Hearts were illuminated at 360 nm, and fluorescence was recorded simultaneously at 400 and 550 nm. The F4N/F550 fluorescence ratio was calculated by an analog circuit that allowed cancelation of small movement artifacts that were present at single wavelengths. Clear [Ca2+] METHODSAlbino male New Zealand rabbits weighing between 1.8 and 2.2 kg were sacrificed by cervical fracture. The heart was rapidly excised and perfused with a saline solution at a constant aortic flow rate of 20-30 ml/min. The perfusate contained 115 mM NaCl, 4.7 mM KCI, 2.0 mM CaC12, 0.7 mM MgCl2, 28 mM NaHCO3, 0.5 mM NaH2PO4, 20 mM glucose, 10 units of insulin per liter, and 0.1% fetal calf serum adjusted to pH 7.4, equilibrated with 95% 02/5% C02, and heated to maintain epicardial temperature at 30'C + 1PC. Contractions of the left ventricle were measured with an intracavitary latex balloon that contained a fiber-optic pressure transducer (Camino Laboratories) or with an epicardial strain gauge that had the advantage of monitoring wall stress near the site at which fluorescence was measured. The left ventricle was vented by a small polyethylene catheter that drained thebesian vein flow. Some hearts were paced at 180/min by an epicardial plunge electrode.Fluorescence excitation was provided by a 100-W Hg vapor lamp. Illumination was filtered at 360 ± 5 nm and directed through a silica fiber-optic cable onto a circular region of epicardium 1 cm in diameter. Movement artifact was minimized by attachment of the fiber-optic cables to the heart using a plastic hub and rubber girdle. Fluorescence was collected by a ring of eight coaxial fiber-optic cables, divided by a beam splitter, and then filtered at 400 ± 12.5 nm and 550 ± 20 nm before reaching photomultiplier tubes (Hamamatsu). The above emission wavelengths were found to give clearer fluorescence transients than the in vitro fluorescence maxima of indo-1 (Ca2' bound = 405 nm; Ca2+ free = 480 nm). Our chosen emission wavelengths allow greater rejection of the noncalcium-dependent fluorescence of unhydrolyzed indo-1 AM (fluorescence maximum = 450 nm), which is retained in tissue after loading (9). Photomultiplier output at the two emission wavelengths was entered into an electronic ratio circuit and the fluorescence ratio, F4w/F550, was displayed on a strip-chart recorder.Indo-1 AM was solubilized in a mixture of dimethyl sulfoxide/pluronic F-127 (25%, wt/vol), 1 ml of which was added to 400 ml of Tyrodes solution containing 5% fetal calf serum. The final concentration of indo-1 AM was 2.5 AM.Perfusion with indo-1 AM continued for 30 min; this was followed by a 30-min washout. This method of indicator loading produced a 5-to 12-fold increase in fluorescence at Abbreviation: [Ca21],, ...

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Section: Discussionmentioning

confidence: 82%

Cytosolic calcium transients from the beating mammalian heart.

Lee

Smith

Mohabir

et al. 1987

Proc. Natl. Acad. Sci. U.S.A.

134

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“…7G,H ). Because of the rapid association kinetics of Ca 2ϩ binding to indo-1 (k on ϭ 5 ϫ 10 8 M/sec; Jackson et al, 1987), it is unlikely that the slow rise in the reported [Ca 2ϩ ] i is attributable to the inability of the Ca 2ϩ indicator dye to follow the rise in bulk [Ca 2ϩ ] i . Moreover, because of the discrepancy in the kinetics of the bulk [Ca 2ϩ ] i and I BK , these results suggest that at least a fraction of the BK channels in somatotrophs responds to the rapid, high-amplitude increase in submembrane [Ca 2ϩ ] i in the vicinity of the VGCC (heretofore referred to as the domain [Ca 2ϩ ] i ).…”

Section: Rapid Activation Of Bk Channels By Domain [Ca 2؉ ] Imentioning

confidence: 99%

Paradoxical Role of Large-Conductance Calcium-Activated K⁺(BK) Channels in Controlling Action Potential-Driven Ca²⁺Entry in Anterior Pituitary Cells

2001

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Activation of high-conductance Ca 2ϩ -activated K ϩ (BK) channels normally limits action potential duration and the associated voltage-gated Ca 2ϩ entry by facilitating membrane repolarization. Here we report that BK channel activation in rat pituitary somatotrophs prolongs membrane depolarization, leading to the generation of plateau-bursting activity and facilitated Ca 2ϩ entry. Such a paradoxical role of BK channels is determined by their rapid activation by domain Ca 2ϩ , which truncates the action potential amplitude and thereby limits the participation of delayed rectifying K ϩ channels during membrane repolarization. Conversely, pituitary gonadotrophs express relatively few BK channels and fire single spikes with a low capacity to promote Ca 2ϩ entry, whereas an elevation in BK current expression in a gonadotroph model system leads to the generation of plateaubursting activity and high-amplitude Ca 2ϩ transients.

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“…The 'effective' on and off rate constants for Ca2+ binding of Fura-2-loaded skeletal muscle fibres were 4-6 times smaller than those in vitro (2-7 x 108 M-1 s-1 and 84-97 s-1 respectively, Jackson, Timmerman, Bagshaw & Ashley, 1987;Kao & Tsien, 1988) due to binding of Fura-2 to the cytoplasmic proteins . If such a binding occurred in the ganglion cell, Focal depth for objectives used in epifluorescence measurements (Methods A and B) was measured by recording fluorescence from a drop of a Fura-2 solution (5 FM) placed in a plane (less than 2,um in thickness and 50 um in diameter) at different levels of the microscope stage ( Fig.…”

Section: Measurements Of Fura-2 Fluorescencementioning

confidence: 99%

Intracellular calcium dynamics in response to action potentials in bullfrog sympathetic ganglion cells.

Nohmi

Hua

Kuba

1992

The Journal of Physiology

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SUMMARY1. Dynamic changes in the intracellular free Ca2" concentration ([Ca2`]j) following electrical membrane activity, were recorded from the neurone soma of the excised bullfrog sympathetic ganglion, using Fura-2 fluorescence and compared with the accompanying Ca2+-dependent electrical membrane responses. 7. Ryanodine (10-50 aM) did not affect tetanus-induced Ca2+ transients, whereas it blocked completely the caffeine-induced oscillation of [Ca2+]i.8. Ca2+ transients induced by a tetanus in Ringer solution were independent of the interval from the preceding tetanus. The amplitude of Ca2+ transients induced by a tetanus in the presence of caffeine (5 mM) was equal to, or greater than, that generated in Ringer solution in any of the phases of [Ca2+]i oscillation.9. It is suggested that under the physiological conditions here, the induction of action potentials does not cause the release of Ca2+ in the cells of the freshly excised bullfrog sympathetic ganglion, and that Ca2+-buffering systems contribute not only to lowering a transient rise in [Ca2+]i but also to sustaining an increased [Ca2+]i after a large Ca2+ load into the cell.

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The kinetics of calcium binding to fura‐2 and indo‐1

Cited by 125 publications

References 11 publications

Cytosolic calcium transients from the beating mammalian heart.

Cytosolic calcium transients from the beating mammalian heart.

Paradoxical Role of Large-Conductance Calcium-Activated K⁺(BK) Channels in Controlling Action Potential-Driven Ca²⁺Entry in Anterior Pituitary Cells

Intracellular calcium dynamics in response to action potentials in bullfrog sympathetic ganglion cells.

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The kinetics of calcium binding to fura‐2 and indo‐1

Cited by 125 publications

References 11 publications

Cytosolic calcium transients from the beating mammalian heart.

Cytosolic calcium transients from the beating mammalian heart.

Paradoxical Role of Large-Conductance Calcium-Activated K+(BK) Channels in Controlling Action Potential-Driven Ca2+Entry in Anterior Pituitary Cells

Intracellular calcium dynamics in response to action potentials in bullfrog sympathetic ganglion cells.

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Paradoxical Role of Large-Conductance Calcium-Activated K⁺(BK) Channels in Controlling Action Potential-Driven Ca²⁺Entry in Anterior Pituitary Cells