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  • 1
    ISSN: 1432-2013
    Keywords: Lacrimal gland ; Cl− activity ; Acetylcholine ; Cl− permeability ; Ca2+ ionophore
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Using double-barreled Cl−-sensitive microelectrodes, intracellular Cl− activity (A Cl i ) in the mouse lacrimal acinar cells in vitro was determined in both resting and secretory phases. In the resting stateA Cl i was 31 mmol/l which was 1.4 times higher than that predicted for the passive distribution according to the membrane potential (V m) of −41 mV. Addition of acetylcholine (ACh, 1μM) hyperpolarizedV m to −63 mV and decreasedA Cl i to 20 mmol/l which was still twice the equilibrium activity. A-23178 produced similar changes inV m andA Cl i to those induced by ACh. It was concluded that Cl− was actively accumulated in the acinar cells and, in the secretory phase, Cl− efflux was enhanced by the increased driving force and Ca2+-mediated increase in the Cl− permeability across the cell membrane.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2013
    Keywords: Na+/H+ exchange ; Intracellular pH regulation ; Salivary gland ; Protein kinase C ; Intracellular Ca2+ ; Acetylcholine ; Ionomycin ; Phorbol esters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The mechanism of regulation of intracellular pH (pHi) in dispersed acini from the rat mandibular salivary gland has been studied with a microfluorimetric imaging method and the pH probe 2′,7′-bis(2-carboxyethyl)-5(and −6)-carboxyfluorescein. The pHi in the TRIS/HEPES-buffered standard solution was 7.29±0.01. Addition of 1 μmol/l acetylcholine (ACh) or ionomycin caused a sustained increase in the pHi. These agents decreased pHi in the absence of external Na+ or in the presence of amiloride. The rate of pHi recovery from an acid load after NH 4 + prepulse was a linear function of pHi and increased as pHi became more acidic. Addition of ACh shifted the relationship towards a more alkaline pHi range. The increase in pHi induced by ACh or ionomycin was not inhibited by the protein kinase C inhibitors staurosporine (10 nM) and 1-(5-isoquinolinesulfonyl)-1-methylpiperazine (50 μmol/l). Addition of 0.1–1 μmol/l phorbol 12-myristate 13-acetate (TPA) had little effect on pHi within 10 min; however, exposure to TPA for 120 min resulted in a significant rise in pHi. In Ca2+-free solution with 50 μmol/l 8-(diethylamino)-octyl-3,4,5-trimethoxybenzoate, the ACh-induced rise in both pHi and cytosolic Ca2+ concentration was suppressed. ACh and ionomycin caused an increment of amiloride-sensitive acid output into the extracellular fluid, while 20 μmol/l 1-oleoyl-2-acetylglycerol had little effect on it. It was concluded that (a) stimulation with ACh activated the Na+/H+ antiport in the plasma membrane, (b) ACh also stimulated the intracellular acid production but acid extrusion by the Na+/H+ antiport prevented the cell from intracellular acidification, and (c) the major route of signal transduction for the ACh-induced activation of the Na+/H+ antiport was independent of protein kinase C but was dependent on the rise in cytosolic Ca2+ concentration. The implication of the cytosolic acidification and cell volume change in pHi regulation is discussed.
    Type of Medium: Electronic Resource
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