Morphine induces an intracellular alkalinization in bovine aortic endothelial cells (BAECs).
Juliann Gong Kiang, Margaret Colden‐Stanfield
Abstract
Juliann Gong Kiang, Margaret Colden‐Stanfield
Abstract
The resting intracellular pH (pHi) of BAECs, by using BCECF fluorescence, at 37 degrees C in Na+ Hanks' was 7.22 +/- 0.03. Cells which had been acid-loaded recovered from the intracellular acidification in Na+ Hanks' in a [Na+]o-dependent and amiloride-sensitive manner. Recovery from acidification had an apparent Km for Na+ of 40 +/- 10 mM and Ki for amiloride of 26 +/- 4 microM. Morphine (50 microM, 20 min, 37 degrees C) increased the pHi to 7.55 +/- 0.05. Naloxone (50 microM) given 5 min before morphine (50 microM) blocked this effect, indicating that this was an opiate receptor-mediated phenomenon. To determine if morphine activated the Na+/H+ exchanger, pHi was monitored in Na+-free Hanks', acidic Na+ Hanks' or amiloride-containing Na+ Hanks'. The alkalinization produced by morphine was not observed under all these circumstances. These data suggest morphine activates the Na+/H+ exchanger via opiate receptors.
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The resting intracellular pH (pHi) of BAECs, by using BCECF fluorescence, at 37 degrees C in Na+ Hanks' was 7.22 +/- 0.03. Cells which had been acid-loaded recovered from the intracellular acidification in Na+ Hanks' in a [Na+]o-dependent and amiloride-sensitive manner. Recovery from acidification had an apparent Km for Na+ of 40 +/- 10 mM and Ki for amiloride of 26 +/- 4 microM. Morphine (50 microM, 20 min, 37 degrees C) increased the pHi to 7.55 +/- 0.05. Naloxone (50 microM) given 5 min before morphine (50 microM) blocked this effect, indicating that this was an opiate receptor-mediated phenomenon. To determine if morphine activated the Na+/H+ exchanger, pHi was monitored in Na+-free Hanks', acidic Na+ Hanks' or amiloride-containing Na+ Hanks'. The alkalinization produced by morphine was not observed under all these circumstances. These data suggest morphine activates the Na+/H+ exchanger via opiate receptors.
Key concepts: Amiloride, Intracellular pH, Sodium–hydrogen antiporter, Morphine, Chemistry, Intracellular, (+)-Naloxone, Sodium