AJP - Cell Physiology, Vol 264, Issue 5 C1345-C1349, Copyright © 1993 by American Physiological Society
A dramatic pH-dependent alteration in ANP receptor density: a note for using cultured cells
T. Katafuchi, H. Hagiwara, T. Ito and S. Hirose
Department of Biological Sciences, Tokyo Institute of Technology, Japan.
Culture media tend to become acidic when rapidly growing cells are cultured
under batch conditions using a CO2/HCO3- buffer system. The effects of this
inherent lowering of pH on cellular makeup of cultured cells, which have
long been ignored, were examined by monitoring the pH and number of the
atrial natriuretic peptide (ANP) receptors expressed on the cultured bovine
endothelial cells. The Eagle's minimum essential medium was adjusted to
three different pH values of 7.0, 7.4, and 7.7 and used for 48-h batch
cultures. After this 48-h incubation, the pH values of the media were found
to be 7.0, 7.1, and 7.4, respectively. These pH shifts had unexpectedly
strong influences on the ANP receptor levels without affecting the
affinity. Cells maintained in the slightly higher pH medium had a trace
amount of the receptor (< 10 sites/cell), while those in the lower pH
environment exhibited a large number of binding sites (40,000 sites/cell).
Similar situations might occur in other cellular components and in other
types of cells, and therefore, such possibilities should be kept in mind
when cultured cell systems are used.
