Calcium, magnesium, and growth control in the WI-38 human fibroblast cell.

Abstract

WI 38 and SV40[transformed]WI-38 cells were synchronized using centrifugal elutriation. This technique allows for the rapid harvesting of early G1 phase cells from exponentially growing populations of both the normal and transformed cell. Using these cells, and WI-38 cells synchronized by serum deprivation, the effects of extracellular Ca and Mg levels on the progression of cells through G1 phase were studied. A differential sensitivity to both Ca and Mg deprivation is observed between normal and transformed cells. The WI-38 cell requires higher levels of both ions for traversal of G1 phase and for continued proliferation as compared to the transformed cell. The temporal nature of the Ca and Mg requirements for the WI-38 cell was examined during G1 phase. Ca is strictly required during early and late G1 phase, but not necessarily throughout mid-G1. An early and late G1 Ca requirement is found in serum-stimulated WI-38 cells. The Mg requirement of WI-38 cells does not appear to be temporally well-defined. Mg appears to be a permissive factor, required throughout G1 phase rather than at certain prescribed intervals. These two cations probably do not exert their effects on cell growth entirely through a common competitive mechanism. Ca appears to be involved in early serum or growth factor-mediated G1 events and later pre-S-phase events, as suggested in previous studies on other cell lines.