Studies of the mechanism of activation of HIT-T15 cells by lactate

• Published in: Biochimica et biophysica acta Vol. 1091; no. 2; pp. 141 - 144
• Main Authors: Lynch, Angela M., Trebilcock, Richard, Tomlinson, Stephen, Best, Leonard
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 31.01.1991; Elsevier Science
• Subjects: Acetates - pharmacology; Aminoquinolines; Animal cells; Animals; Beta-cell; Biological and medical sciences; Calcium - metabolism; Cation permeability; Cell cultures. Hybridization. Fusion; Cytosol - metabolism; Cytosolic calcium; Depolarization; Fluoresceins; Fundamental and applied biological sciences. Psychology; HIT-T15 cell; Hydrogen-Ion Concentration; Insulinoma - metabolism; Islets of Langerhans - metabolism; Isoxazoles; Lactate; Lactates - pharmacology; Lactic Acid; Membrane Potentials; Molecular and cellular biology; Propionates - pharmacology; Tumor Cells, Cultured - drug effects; Depolarization; HIT-T15 cell; Cytosolic calcium; Beta-cell; Lactate; Cation permeability; Cell culture; Cell line; Calcium; Insulinoma; Plasma membrane; Ion transport; Lactic acid; Fluorescence spectrometry
• ISSN: 0167-4889; 0006-3002; 1879-2596
• DOI: 10.1016/0167-4889(91)90053-Z

l-Lactate, d-lactate, propionate and acetate (all 20 mM) caused a marked intracellular acidification in HIT-T15 cells loaded with 2′7′-bis(car☐yethyl)-5′(6′)-car☐yfluorescein (BCECF), followed by recovery to more alkaline values. The effects of l- and d-lactatee, but not propionate or acetate, were inhibited by 5 mM α-fluorocinnamate. Both l- and d-lactate caused a marked depolarisation and rise in cytosolic [Ca 2+] in HIT cells as assessed by oxonol-V and quin2 fluorescence, respectively. Propionate had similar, though less marked, effects, whereas acetate exerted only a modest influence on membrane potential and cytosolic [Ca 2+]. The rate of oxidation of l-lactate by HIT cells greatly exceeded that of d-lactate. α-Fluorocinnamate delayed, but did not prevent, the effects of l-lactate on HIT cell membrane potential or cytosolic [Ca 2+]. l-lactate diminished the rate of efflux of 86Rb + from preloaded HIT cells. Inhibition of calcium- and nucleotide-sensitive K + channels with tetraethylammonium and tolbutamide also reduced the 86Rb + efflux rate, and prevented any further reduction in response to l-lactate. However, such inhibition of K + channels did not prevent a further depolarisation and rise in cytosolic [Ca 2+] upon the subsequent addition of lactate. It is suggested that the activation of HIT-T15 cells by lactate is not the result of intracellular acidification or increased metabolic flux, and does not require diminished K + permeability. An alternative mechanism is based upon the possible electrogenic flux of lactate across the plasma membrane.