Multiplication of single mammalian cells in a nonbicarbonate medium

The bicarbonate ion is essential for efficient DNA synthesis by primary cultured rat hepatocytes

Bicarbonate in the culture medium is essential for DNA synthesis of primary cultured rat hepatocytes stimulated by epidermal growth factor (EGF). When primary cultured hepatocytes in supplemented Leibovitz L15 medium were placed in a 100% air incubator, no increase in DNA synthesis was observed even after stimulation by EGF. However, when these cells were cultured with NaHCO3 and EGF and placed in a 5% CO2:95% air incubator, a stimulus of DNA synthesis more than 10-fold greater than in cultures in air only was seen, and many mitotic figures could be identified. Furthermore, NaHCO3 added to supplemented DMEM/F12 medium enhanced the DNA synthesis of primary cultured rat hepatocytes in this medium. The ideal pH of the medium for DNA synthesis of cultured hepatocytes was in the range of 7.6 to 8.0. A dose response of NaHCO3 in several media showed that DNA synthesis of the cells increased as the concentration of NaHCO3 increased and that 25 to 30 mM NaHCO3 in the medium was optimal for the replication of DNA by primary cultured rat hepatocytes.

Regulation of glucose utilization in chick embryo fibroblasts by bicarbonate ion

The amount of glucose consumed by chick embryo fibroblasts in primary culture is strongly influenced by the presence of bicarbonate ion in the culture medium. Cells grown on glucose at physiologic concentration (5.5 mm) and in the absence of bicarbonate ion have a reduced rate of glucose utilization when compared to their counterparts cultivated in medium containing the usual 25 mM bicarbonate. The presence or absence of bicarbonate is without effect on chick embryo fibroblast proliferation over a 6-day growth period. Both lactic acid accumulation per mole of glucose consumed and the utilization of glutamine increase as a function of bicarbonate ion in the growth medium.

Amphibian cells in culture. I. Nutritional studies

Nutritional requirements of amphibian cells in culture were studied for the purpose of modifying a minimal medium in which frog cells could proliferate and which could be used for obtaining drug-resistant and auxotrophic variants. The serum, purine, CO2, and amino acid requirements for ICR 2A (a Rana pipiens haploid cell strain) have been investigated employing two different media: L-15, a nonbicarbonate, amino acid-buffered medium and Eagle's MEM, a bicarbonate-buffered medium. In this paper we present evidence to support the following conclusions: (1) With L-15 as the base medium, 10% fetal calf serum (FCS) supports optimal cell growth during exponential phase. Calf serum, whole, dialyzed, or heat-inactivated, cannot substitute for FCS and, in fact, is inhibitory. (2) Purines are required by ICR 2A cells only if grown in a nonbicarbonate-buffered medium, since the cells under these conditions cannot produce enough endogenous CO2 to support de novo purine synthesis. (3) In addition to the amino acids considered essential for mammalian cells in culture, ICR 2A cells depend upon exogenous asparagine. Glutamine and/or aspartic acid cannot replace the asparagine requirement. However, ICR 2A cells do utilized exogenous glutamine as an oxidative substrate.