The N‐linked glycosylation of the recombinant protein mouse placental lactogen‐I (mPL‐I) expressed by Chinese hamster ovary (CHO) cells under nongrowth conditions was inhibited by increasing levels of ammonium chloride (3 and 9 mM) in a serum‐free, protein expression medium. The effect of ammonia on glycosylation was dependent on the extracellular pH (pHe). In media containing 0 and 9 mM ammonium chloride, the percentage of the most heavily glycosylated forms of secreted mPL‐I decreased from ca. 90% to ca. 25% at pHe 8.0, and from ca. 90% to ca. 65% at pHe 7.6, respectively. However, at pHe 7.2, the most heavily glycosylated forms of secreted mPL‐I decreased from ca. 90% to ca. 80% in media containing 0 and 9 mM ammonium chloride, respectively. Inhibition of mPL‐I glycosylation was found to correlate with the calculated concentrations of the ammonia species (NH3). Control experiments showed that the ammonia effect on mPL‐I glycosylation could not be attributed to increased chloride concentration or osmolarity, or to extracellular events after secretion of the recombinant protein into the supernatant. Ammonium chloride, 9 mM, inhibited the expression rate of MPL‐I by CHO cells at low pHe. © 1994 John Wiley & Sons, Inc.
- CHO cells
- placental lactogen
- recombinant protein expression
ASJC Scopus subject areas
- Applied Microbiology and Biotechnology