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Effects of acidic pH on the formation of vinblastine‐induced paracrystals in Chinese hamster ovary cells
Author(s) -
Takanari Hideki,
Morita Joji,
Yamanaka Hidetaka,
Yada Kenichiro,
Takahashi Asahiko,
Izutsu Kosaku
Publication year - 1994
Publication title -
biology of the cell
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.543
H-Index - 85
eISSN - 1768-322X
pISSN - 0248-4900
DOI - 10.1016/0248-4900(94)90066-3
Subject(s) - chinese hamster ovary cell , biophysics , cytoplasm , microtubule , crystallization , sodium azide , tubulin , cytoskeleton , biology , chinese hamster , vinblastine , intracellular , crystallography , chemistry , biochemistry , in vitro , microbiology and biotechnology , cell , genetics , receptor , organic chemistry , chemotherapy
Summary— The pH‐related change in morphology of vinblastine (VLB)‐induced paracrystals formed in Chinese hamster ovary (CHO) cells was examined immunohistochemically in order to determine both the mechanism of tubulin crystallization and the influence of acidic pHs on cytoskeletal microtubules. Lowering the extracellular pH (pHe) rapidly reduced the intracellular pH (pHi) in CHO cells. Lowering the pHi to near the neutral range significantly accelerated the growth of VLB‐induced paracrystals, compared to that of paracrystals formed at a physiological pHe. However, further cytoplasmic acidification caused by the addition of sodium azide into the culture medium induced the disappearance of typical paracrystals and the appearance of a highly organized meshwork of tubulin appearing as short, thick filaments at the light microscopic level. Treatments using different concentrations of VLB at different pHe's showed that low pHi's (6.7 and 6.3) suppressed paracrystal‐formation at lower concentrations of VLB (5×10 −6 M and 10 −5 M). At higher concentrations of VLB (5×10 −5 M and 10 −4 M), only short filaments were formed at pHi 6. 3. Electron microscopy revealed that the filaments had a ladder‐like structure probably consisting of a stacked series of fused rings. This indicates that paracrystals may be modified by extremely low pH. These results show that paracrystals are unstable in living cells and that their formation is regulated by environmental pH.