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Cell cycle regulation by environmental pH
Author(s) -
Taylor Ian W.,
Hodson Pamela J.
Publication year - 1984
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041210310
Subject(s) - extracellular , elutriation , cell cycle , biology , cell growth , exponential growth , cell culture , microbiology and biotechnology , cell , cell division , restriction point , dna synthesis , dna , biochemistry , biophysics , chemistry , cell cycle progression , genetics , mathematical analysis , mathematics , organic chemistry
Purified populations of quiescent human tumour cells were isolated from plateau phase cultures of PMC‐22 cells by centrifugal elutriation. Dilution into fresh medium resulted in these quiescent cells entering S phase exponentially with a t1/2 of 12 hr, after a 18‐20‐hr lag period during which cellular RNA content increased. Subsequent studies showed that recruitment of quiescent cells into the cell cycle could be regulated by extracellular pH. When exponentially growing PMC‐22 cells were exposed to acidic extracellular pH levels, three growth patterns were observed: (1) Normal growth between pH 7.2 to pH 6.8; (2) A reduction in growth rate associated with accumulation of cells with a G 1 DNA content between pH 6.7 and 6.4 (this was also shown to occur in a number of other tumour cell lines); (3) Non‐cell‐cycle‐phase‐specific arrest of growth at pH levels less than 6.3. Further studies with purified quiescent cell populations showed the possible existence of a pH‐dependent restriction point in the G 1 phase of these tumour cells. The implications of these observations to tumour biology are discussed.