Transient responses of hybridoma cells to nutrient additions in continuous culture: I. Glucose pulse and step changes

Abstract

Glucose and glutamine are the main nutrients used by mammalian cells in culture. Each provides unique biosynthetic precursors but are complementary for production of other metabolites and energy. The transient and steady-state responses of hybridoma growth and metabolism to glucose pulse and step changes have been examined. Metabolic quotients are reported for oxygen, glucose, lactate, ammonia, glutamine, alanine, and other amino acids. The glucose consumption rate increased by 100-200% immediately after glucose was added to the reactor, and the increased glycolytic ATP production appears to be responsible for the concurrent rapid decrease in the oxygen consumption rate. The effects on glutamine consumption were delayed, probably due to buffering by the TCA cycle and interrelated pathways. A period of increased biosynthetic activity, as evidenced by an increase in the estimated specific ATP production rate and lower by-product yields from glutamine, preceded the increase in cell concentration after the glucose step change. The biosynthetic yield of cells from ATP was calculated, and it was estimated that maintenance accounted for about 60% of the energy used by the cells at a specific growth rate of 0.66 day(-1). The estimated 22% ATP production due to glycoysis was twice as great as that before the step change.

Determination of the respiration quotient in mammalian cell culture in bicarbonate buffered media

“…At different steady states the specific OUR will only increase at very low levels of glucose and is independent from glutamine concentrations. 7,8 In our case, we found a linear relationship between cell density and (volumetric) OUR at a high correlation (r2 = 0.9264, n = 11) in continuous culture with residual glucose concentrations >0.6 mM. We suggest that, under certain well-defined conditions, the volumetric OUR and the RQ might be useful parameters as an indication of both the cell density (volumetric OUR) and the physiological state of the cells (RQ).…”

The transient responses of hybridoma cells to nutrient additions in continuous culture: II. Glutamine pulse and step changes

“…The maintenance energy qATF' (~/ y n , A T p ) + mATP (1) When written in terms of cell number, this equation is only valid at steady state, as evidenced by the delay before increased growth rate [ Fig. 8(a)] after the increase in qATp (Fig.…”

Bcl-2 over-expression reduces growth rate and prolongs G1 phase in continuous chemostat cultures of hybridoma cells

“…Balances on X MI (membrane-intact cells) and X MD (membrane-damaged cells as revealed by trypan blue staining) allow determination (following Miller et al (1988)) of the death rate constant K d , defined by transition from the one state to the other (and assumed to be first order in X MI ) as follows:…”