title: Mathematical modeling of the effects of ammonium ion on the intracellular pH of hybridoma cells.
abstract: A mathematical model for the effects of NH(4)Cl addition to the growth medium on hybridoma cell intracellular pH (pH(i)) is presented which includes a detailed description of the properties of the Na(+)/H(+) exchanger. The model is used to calculate the steady-state value of pH(i) as a function of the extracellular NH(4)Cl concentration, employing parameter values taken from the literature except for the cell permeability to NH(4) (+) This parameter value, estimated to be 3.5 x 10(-7) cm/s, is obtained by fitting simulation results to experimental data obtained previously for the steady-state value of pH(i) in the presence of 10mM NH(4)Cl. The model simulates well the major features of previously observed experimental pH(i) changes following NH(4)Cl addition: the transient characteristics, dependence on the NH(4)Cl concentration, and lack of dependence on the external pH value. The effect of parameter variations on model results is also investigated in additional simulations. The general modeling framework employed here should be useful for other types of mammalian cells.
authors.affiliation: Department of Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: A
authors.initials: A
authors.lastname: McQueen
authors.forename: J E
authors.initials: JE
authors.lastname: Bailey