Calcium release-activated calcium current in rat mast cells

• Published in: The Journal of physiology Vol. 465; no. 1; pp. 359 - 386
• Main Authors: Hoth, M, Penner, R
• Format: Journal Article
• Language: English
• Published: Oxford The Physiological Society 01.06.1993; Blackwell
• Subjects: Animals; Biological and medical sciences; Calcium - metabolism; Calcium Channel Blockers - pharmacology; Calcium Channels - drug effects; Calcium Channels - metabolism; Cations, Divalent - pharmacology; Cations, Monovalent - metabolism; Cations, Monovalent - pharmacology; Cell Membrane - drug effects; Cell Membrane - metabolism; Cells, Cultured; Chelating Agents - pharmacology; Fundamental and applied biological sciences. Psychology; Fundamental immunology; Fura-2; Immunobiology; Inosine Triphosphate - pharmacology; Kinetics; Male; Mast Cells - drug effects; Mast Cells - metabolism; Membrane Potentials - physiology; Myeloid cells: ontogeny, maturation, markers, receptors; Peritoneal Cavity - cytology; Polynuclears; Rats; Rats, Wistar; Calcium; Rat; Rodentia; Granulocyte; Electrophysiology; Ion transport; Patch clamp method; Ionic current; Myeloid cell; Signal transduction; Vertebrata; Mammalia; Mast cell; Kinetics
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1113/jphysiol.1993.sp019681

1. Whole-cell patch clamp recordings of membrane currents and fura-2 measurements of free intracellular calcium concentration ([Ca2+]i) were used to study the biophysical properties of a calcium current activated by depletion of intracellular calcium stores in rat peritoneal mast cells. 2. Calcium influx through an inward calcium release-activated calcium current (ICRAC) was induced by three independent mechanisms that result in store depletion: intracellular infusion of inositol 1,4,5-trisphosphate (InsP3) or extracellular application of ionomycin (active depletion), and intracellular infusion of calcium chelators (ethylene glycol bis-N,N,N',N'-tetraacetic acid (EGTA) or 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA)) to prevent reuptake of leaked-out calcium into the stores (passive depletion). 3. The activation of ICRAC induced by active store depletion has a short delay (4-14 s) following intracellular infusion of InsP3 or extracellular application of ionomycin. It has a monoexponential time course with a time constant of 20-30 s and, depending on the complementary Ca2+ buffer, a mean normalized amplitude (at 0 mV) of 0.6 pA pF-1 (with EGTA) and 1.1 pA pF-1 (with BAPTA). 4. After full activation of ICRAC by InsP3 in the presence of EGTA (10 mM), hyperpolarizing pulses to -100 mV induced an instantaneous inward current that decayed by 64% within 50 ms. This inactivation is probably mediated by [Ca2+]i, since the decrease of inward current in the presence of the fast Ca2+ buffer BAPTA (10 mM) was only 30%. 5. The amplitude of ICRAC was dependent on the extracellular Ca2+ concentration with an apparent dissociation constant (KD) of 3.3 mM. Inward currents were nonsaturating up to -200 mV. 6. The selectivity of ICRAC for Ca2+ was assessed by using fura-2 as the dominant intracellular buffer (at a concentration of 2 mM) and relating the absolute changes in the calcium-sensitive fluorescence (390 nm excitation) with the calcium current integral. This relationship was almost identical to the one determined for Ca2+ influx through voltage-activated calcium currents in chromaffin cells, suggesting a similar selectivity. Replacing Na+ and K+ by N-methyl-D-glucamine (with Ca2+ ions as exclusive charge carriers) reduced the amplitude of ICRAC by only 9% further suggesting a high specificity for Ca2+ ions. 7. The current amplitude was not greatly affected by variations of external Mg2+ in the range of 0-12 mM. Even at 12 mM Mg2+ the current amplitude was reduced by only 23%. 8. ICRAC was dose-dependently inhibited by Cd2+.