Hydrogen-Deuterium Exchange Effects on β-Endorphin Release from AtT20 Murine Pituitary Tumor Cells

Masayuki Ikeda, Shigeru Suzuki, Masahiro Kishio, Moritoshi Hirono, Takashi Sugiyama, Junko Matsuura, Teppei Suzuki, Takayuki Sota, Charles N. Allen, Shiro Konishi, Tohru Yoshioka

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


Abundant evidences demonstrate that deuterium oxide (D2O) modulates various secretory activities, but specific mechanisms remain unclear. Using AtT20 cells, we examined effects of D2O on physiological processes underlying β-endorphin release. Immunofluorescent confocal microscopy demonstrated that 90% D2O buffer increased the amount of actin filament in cell somas and decreased it in cell processes, whereas β-tubulin was not affected. Ca2+ imaging demonstrated that high-K+-induced Ca2+ influx was not affected during D 2O treatment, but was completely inhibited upon D2O washout. The H2O/D2O replacement in internal solutions of patch electrodes reduced Ca2+ currents evoked by depolarizing voltage steps, whereas additional extracellular H2O/D2O replacement recovered the currents, suggesting that D2O gradient across plasma membrane is critical for Ca2+ channel kinetics. Radioimmunoassay of high-K+-induced β-endorphin release demonstrated an increase during D2O treatment and a decrease upon D2O washout. These results demonstrate that the H 2O-to-D2O-induced increase in β-endorphin release corresponded with the redistribution of actin, and the D2O-to-H 2O-induced decrease in β-endorphin release corresponded with the inhibition of voltage-sensitive Ca2+ channels. The computer modeling suggests that the differences in the zero-point vibrational energy between protonated and deuterated amino acids produce an asymmetric distribution of these amino acids upon D2O washout and this causes the dysfunction of Ca2+ channels.

Original languageEnglish (US)
Pages (from-to)565-575
Number of pages11
JournalBiophysical Journal
Issue number1 I
StatePublished - Jan 2004

ASJC Scopus subject areas

  • Biophysics


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