CULTURE PH AFFECTS EXPRESSION RATES AND GLYCOSYLATION OF RECOMBINANT MOUSE PLACENTAL-LACTOGEN PROTEINS BY CHINESE-HAMSTER OVARY (CHO) CELLS

Glycosylation patterns and specific expression rates of the recombinant protein mouse placental lactogen-I (mPL-I) by Chinese hamster ovary (CHO) cells varied significantly over the extracellular pH (pH(e)) range of 6.1 to 8.7. The maximum specific mPL-I expression rates occurred between pH(e) 7.6 and 8.0. The pH(e) effect on protein expression was confirmed using a different CHO cell expressing the unglycosylated recombinant protein mouse placental lactogen-II (mPL-II). Decreases in the extent of glycosylation of mPL-I were observed at low (below 6.9) and high (above 8.2) pH(e) values. The pH(e) dependent variations in mPL-I accumulation in the supernatant as well as in glycosylation patterns were not the result of enzymatic degradation in the culture medium.