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Isolated ductal cells of rat submandibular gland phospholipid pools were labeled with [3H]arachidonic acid (AA). The tracer was incorporated preferentially to phosphatidylcholine (46% of the lipidic fraction). Extracellular ATP induced the release of [3H]AA to the extracellular medium in a time- and dose-dependent manner (EC50 = 220 microM). Among other(More)
We have investigated the relevant protease activity in rat liver, which is responsible for most of the receptor-mediated epidermal growth factor (EGF) degradation in vivo. EGF was sequentially cleaved by endosomal proteases at a limited number of sites, which were identified by high performance liquid chromatography and mass spectrometry. EGF proteolysis is(More)
The effect of extracellular ATP on the intracellular calcium concentration ([Ca2+]i) in rat submandibular glands was tested. The dose-response curve for ATP was biphasic with a first increase in the 1-30 microM concentration range and a further increase at concentrations higher than 100 microM. Among ATP analogs, only benzoyl-ATP stimulated the low affinity(More)
The endosomal compartment of hepatic parenchymal cells contains an acidic endopeptidase, endosomal acidic insulinase, which hydrolyzes internalized insulin and generates the major primary end product A(1--21)-B(1--24) insulin resulting from a major cleavage at residues Phe(B24)-Phe(B25). This study addresses the nature of the relevant endopeptidase activity(More)
Secreted Frizzled-related proteins (sFRPs) are modulators of the Wnt signaling pathway that plays important roles in both embryogenesis and oncogenesis. sFRPs have been proposed to antagonize Wnt activity by binding to Wnts. However, the affinity of this binding is unknown. Here we show, using surface plasmon resonance and purified proteins, that sFRP1,(More)
The intracellular concentration of calcium ([Ca2+]i) of rat submandibular ductal cells was measured with the intracellular fluorescent dye Fura-2. Carbachol (100 microM) and ATP (1 mM) both increased the [Ca2+]i. The late response to ATP was blocked by 0.5 mM Ni2+. This concentration of Ni2+ also blocked the increase of the [Ca2+]i and the uptake of(More)
ATP (1 microM-1 mM) increased the intracellular Ca2+ concentration ([Ca2+]i) in rat submandibular ductal cells. The dose-response curve was biphasic with a first plateau approximately 10 microM and a second increase at concentrations higher than 100 microM. This second increase was abolished in the absence of extracellular calcium or in the presence of(More)
The effect of propofol (2,6-diisopropylphenol) on the intracellular concentration of calcium ([Ca(2+)](i)) and on the response of rat submandibular acini to purinergic agonists was studied. By itself, propofol (60 to 200 microM) slowly increased the [Ca(2+)](i) without affecting the production of inositol phosphates. The increase of the [Ca(2+)](i) involved(More)
The intracellular pH (pHi) of rat submandibular cells was measured by 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF). The cells recovered from ammonium (30 mM) prepulse to their resting pHi within 10 min. Ethylisopropylamiloride (EIPA), an inhibitor of the Na+/H+ exchanger, slows the rate of pHi recovery. ATP (1 mM), in the presence of EIPA,(More)
Rat submandibular glands were digested with crude collagenase, and the intracellular calcium concentration of the cellular suspension was measured using fura-2. In the absence of extracellular magnesium and calcium ([Ca2+]o), ATP had no effect; the response to ATP peaked at 1-2.5 mM [Ca2+]o and was inhibited at 5 mM. One millimolar (mM) extracellular ATP(More)