Flow cytometry and Northern blotting were used to examine the effects of hydrodynamic forces in stirred tank bioreactors on CD13 receptor surface content and mRNA levels of HL60 (human promyelocytic leukemia) cells. A step increase in agitation rate from 80 to 300 or 400 rpm reduced the apparent HL60 growth rate in a dose‐dependent manner. This step increase in agitation rate (to 300 or 400 rpm) also increased the CD13 receptor surface content on averge by 30% and 100%, respectively. This increase in CD13 receptor surface content was correlated with a 10% and a 60% increase in CD13 mRNA levels. We also observed a significant and very reproducible drop in CD13 expression over the course of a batch bioreactor run (80 rpm). Although we have no explanation for this, we show that the decrease in CD13 receptor surface content can be (at least partially, if not fully) explained by the corresponding decrease in CD13 mRNA. HL60 cell cultures agitated at 300 and 400 rpm exhibited glucose consumption and lactate production rates that were approximately 40% and 90% greater than values of the cultures agitated at 80 rpm. The physiological and practical implications of these results are discussed. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 239–250, 1998.

Flow cytometry and Northern blotting were used to examine the effects of hydrodynamic forces in stirred tank bioreactors on CD13 receptor surface content and mRNA levels of HL60 (human promyelocytic leukemia) cells. A step increase in agitation rate from 80 to 300 or 400 rpm reduced the apparent HL60 growth rate in a dose-dependent manner. This step increase in agitation rate (to 300 or 400 rpm) also increased the CD13 receptor surface content on averge by 30% and 100%, respectively. This increase in CD13 receptor surface content was correlated with a 10% and a 60% increase in CD13 mRNA levels. We also observed a significant and very reproducible drop in CD13 expression over the course of a batch bioreactor run (80 rpm). Although we have no explanation for this, we show that the decrease in CD13 receptor surface content can be (at least partially, if not fully) explained by the corresponding decrease in CD13 mRNA. HL60 cell cultures agitated at 300 and 400 rpm exhibited glucose consumption and lactate production rates that were approximately 40% and 90% greater than values of the cultures agitated at 80 rpm. The physiological and practical implications of these results are discussed.

Flow cytometry and Northern blotting were used to examine the effects of extracellular pH on CD13 receptor surface content and mRNA levels of HL60 (human promyelocytic leukemia) cells. Decreasing culture pH (7.4, 7.2, and 7.0) increased the CD13 receptor surface content of HL60 cells cultured at low agitation intensity (80 rpm) in 2-L bioreactors. Unlike our earlier findings on the effects of increasing agitation rates and serum concentrations, changes in CD13 receptor content in response to decreasing culture pH did not correlate with changes in CD13 mRNA levels. Decreasing culture pH also decreased the average HL60 cell size. HL60 cells cultured at pH 7.0 and 7.2 exhibited glucose consumption and lactate production rates that were approximately 30-40% and 20-30% lower, respectively, than values of cells cultured at pH 7.4.

No abstract

The effects of serum medium concentration on the CD13 receptor surface content and mRNA levels of HL60 (human promyelocytic leukemia) cells were examined using flow cytometry and Northern blotting. Increasing the serum concentration from 2.5% to 10% and from 5% to 10% increased the CD13 receptor surface content of HL60 cells by 100% and 25%, respectively, in spinner flasks agitated at 60 rpm. In bioreactors at 80 rpm, increasing the serum concentration from 2.5% to 10% and from 5% to 10% increased the CD13 receptor surface content by 60% and 35%, respectively. This increase in CD13 receptor surface content was correlated with a 30% and a 20% increase in CD13 mRNA levels. Increasing serum concentrations also increased the average HL60 cell size under non‐damaging conditions (60 rpm in spinner flasks, 80 rpm in bioreactors). Under conditions of agitation at 300 rpm in 2 L bioreactors, increasing serum concentrations (2.5% vs. 10%, 5% vs. 10%) allowed for higher HL60 apparent growth rates, but decreased the CD13 receptor surface content and mRNA levels. In view of our earlier findings on the effects of agitation on the CD13 antigen, these data suggest that serum reduces the transduction of mechanical forces that affect CD13 expression. At 300 rpm, HL60 cells cultured in 10% serum exhibited glucose consumption and lactate production rates that were approximately 50% and 60% lower than the values of cells cultured in 5% and 2.5% serum, respectively. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 259–268, 1998.